Oh this is amazing! I have a few of their cube routers sitting around and I always hated how app-locked their firmware was when it really is just a wifi repeater with a few extras (mesh) on top. Root access will do wonders to bypassing the app now (and also disabling their ping-for-green-light mechanism which spams the network with a constant dns resolution to microsoft.com lol).
Also honest take this looks less like a "backdoor" (implies malicious - this is a link to a CVE after all) and more like a developer access credential/default credential that was burned into the firmware (i'd imagine the code remains but on a production run they randomize the key so its non-guessable but then you get lazy and dont run that extra step and this slips in/you burn the bare firmware with no production configs).
Hm, do you ever go over 1gbit? If my understanding is correct, good affordable routers like Mikrotik's CCR2004 are fully closed, so the only option is to build your own shitty box which will be much less energy efficient than their specialized switch chips.
Last time when I looked OpenWRT was unable to support MIMO and beamforming capabilities of many of the devices it was running on.
This capabilities are crucial to have decent coverage, signal strength and throughput where I live (i.e.: crowded/congested wireless networks in an apartment complex).
Did OpenWRT team managed to work around them, or did the manufacturers started to play nicer with open drivers with loadable firmware?
Not exposing your management interface to internet and running a guest network which doesn't have access to said management interfaces can block 95%+ of the attacks, I believe.
At that point it’s not even a back door it’s just stupid default root password kind of design which used to be standard in this kind of hardware. Backdoor would at least try to be subtle :)
Maybe it's time to take a closer look at reality and correct this meme, which might casually blur the issue and deflect responsibility?
Looking at the IT security landscape we see every layer, every product category if not every product itself riddled with issues at one point or another. At the same time the incentives to put those security issues in are huge, and we know attackers work systematic, creative and persistent to introduce those weak points.
Security is hard and many bugs certainly happen due to mistakes, but I wouldn't assume that all of those security mishaps stem from an endless series of blunders from "stupid" programmers.
So I would go with “Never attribute to ignorance that which is adequately explained by malice.”
Tenda may just rebrand, right? It seems like many chinese brands will either rebrand or have a 'competing' brand with the same internals but different externals. (I have no idea if Tenda does this, I've just seen it previously. Specifically with security cameras)
I wish the authors provided some method for checking this vulnerability other than fw version. It seems like Tenda could just change the password and say "yep! all safe now"
> the admin password to be 'admin'. They'd often even print it on the device itself.
Yes but aren't you supposed to change that one? The problem with the rzadmin is that it will continue to work even after you change the regular admin one...
It is probably just a brand, like many others, and based on a reference design from the OEM.
I have a small Tenda 5-port gigabit dumb switch. It uses the same switch chip as this TP-Link, just with different branding; even the "SG105" model number is the same:
The consistency with which networking hardware companies produce such garbage is crazy.
And it’s always amateur hour backdoors somehow. If it was something sophisticated they might get a pass on „ok some security agency made them do it probably“
this is definitely a backdoor, not necessarily that they use it to infiltrate users but definitely they put them at risk.
reminds me of a bug I found in some tplink router it compared passwords of 3 different users but that table was empty so basically 15 NULL bytes would log you in as admin lol
Have used their travel wifi product back when hotel wifi was a strange beast. Wouldn't expect to need it now eSIM and ubiquitous internet travel pricing means the hotel wifi may be the LEAST valid path to access things.
I have a free give-away mikrotik unit in the same price bracket (literally free: they were both conference give-aways) it's physically smaller and it runs what appears to be their mainline code. Say what you like about microtik for quality, they provide pretty much every knob and frob you could want.
I’m working on a hotel right now. And I’ve gone to great lengths to make the wifi more secure. Everyone on their own VLAN. Separate PPSK for each room. Credentials are randomly generated and not some ridiculous pattern of last name and room number or similar. We built our own custom access control system, with what at the time was the strongest keycards we could find (mifare desfire ev3), I’m really trying to make a hotel who’s security isn’t such a joke.
My Macbook is permanently locked out of Cox's hotspot system (used in some U.S. hotels) because the password was given to me on a tiny label which I couldn't read as a blind person except through OCR, and the OCR was wrong a few too many times.
As long as I can bind more than one device in my room, and as long as I can "see" the devices amongst themselves, I'd love this. I can imagine people who want inter-room access but they can live through proxies offsite. If I want to do in room sharing, I need in room wifi.
Gets hard when you bring "smart" TV's to the table. They're going to need to expose into this system somewhat 'credential-free' but if you do it off MAC address then a determined user could disconnect, find MAC, clone ...
I stayed at a clinic once, and all the smart TVs were on the same network.. I wonder what would've happened if I streamed a video from my phone to another room's TV.
A quick search reveals several other serious vulnerabilities in Tenda routers that could grant administrator privileges. Therefore, I tend to believe this is due to the company's incompetence and lack of technical skill rather than malicious intent—but it's still a reason to avoid using Tenda products. There's a reason why Tenda's market share is far lower than TP-Link's.
Man, I remember doing this in the late 90s with ipchains as the only way to get a router that didn't cost an arm and a leg. Eventually consumer/prosumer routers came out.
Ryzen 5 with a dual 10Gbps NIC, running Debian. Overkill for a router/firewall, but I run other services on the same hardware including an email stack, Podman containers, and small AI model for use within Home Assistant.
I wouldn't buy new hardware. Any modest machine built in the last decade would do. If possible, get a machine with an internal ATX power supply rather than an external brick, they tend to be more reliable.
If all you need is 1Gpbs and WiFi, OpenWrt on consumer hardware is probably enough though.
I have a Lenovo thin client running Debian as internet gateway/firewall. With some minor modifications and a small low power blower fan you can add a dual sfp pcie card in it (not all versions can, though there are more manufacturers of thin clients with 4x pcie slots). The blower fan is because the main fan stops often and it needs some cooling.
Use openWrt (https://openwrt.org), and use their hardware list to pick a consumer router with the feature set you need that can be flashed to use openWrt.
From what I can see quickly (I haven't looked hard), "sys.rzadmin.password" is only referenced from the login() function of /bin/httpd in the context of retrieving a value. This value is retrieved and compared before the error message "login err: password is wrong." is emitted. I can't find any other reference to code in any part of the firmware that may allow a user to change the default value of "sys.rzadmin.password".
Also for fun there is a function imsd_upload_log_v1 in /bin/imsd that collects SSIDs, MACs, IP addresses, sys.admin.username, sys.rzadmin.username, timezone, and another function imsd_remote_pwd_get in /bin/imsd that retrieves sys.admin.password. Related library /lib/lubucapi.so also looks like a fun binary to inspect more closely as it contains a command set that seemingly allows either cloud management of Tenda routers and/or remote debugging, and possibly is why imsd_remote_pwd_get exists in /bin/imsd
There was a meme going round of a network diagram that layers a Chinese firewall behind a US firewall behind a Russian firewall so they can all block each other countries backdoors.
Not sure if you're joking, but both have already done so. And any US company is subject to secret orders forcing them to implement a backdoor if demanded.
So will this finally be treated as sabotage/criminal hacking, or is it just yet another example of letting manufacturers do whatever they want to their customers without any punishment? Meanwhile if I find and publish the emails of Tenda customers that they accidentally left unprotected, I get raided by the FBI.
I've seen it last night, and I was like wtf?! Frankly, if they tried to build in some backdoor, I bet they would have done it differently, not so obviously. This must have been some sort of stupidity done for testing purposes, and just got buried deep in the code and forgotten.
This is the main reason why you should always use OpenWRT or other opensource router OS. If it gets an issue, at least it would get patched in the next update.
Almost all consumer electronics come with backdoors—especially given the prevalence of computational advertising. Before criticizing Tenda, we ought to clarify whether this is a consumer-facing (2C) or business-facing (2B) product.
Oh this is amazing! I have a few of their cube routers sitting around and I always hated how app-locked their firmware was when it really is just a wifi repeater with a few extras (mesh) on top. Root access will do wonders to bypassing the app now (and also disabling their ping-for-green-light mechanism which spams the network with a constant dns resolution to microsoft.com lol).
Also honest take this looks less like a "backdoor" (implies malicious - this is a link to a CVE after all) and more like a developer access credential/default credential that was burned into the firmware (i'd imagine the code remains but on a production run they randomize the key so its non-guessable but then you get lazy and dont run that extra step and this slips in/you burn the bare firmware with no production configs).
> The associated username is not validated, so any provided username will succeed when paired with the backdoor password.
Great. I am really wondering why should the customers trust these manufacturers.
At this point I would not use any router with vendor-provided black box firmware. Full stop.
I would always install OpenWRT or something similar on it before using it.
And if that is not possible for whatever reason, I would not even think about buying such a device.
Hm, do you ever go over 1gbit? If my understanding is correct, good affordable routers like Mikrotik's CCR2004 are fully closed, so the only option is to build your own shitty box which will be much less energy efficient than their specialized switch chips.
Last time when I looked OpenWRT was unable to support MIMO and beamforming capabilities of many of the devices it was running on.
This capabilities are crucial to have decent coverage, signal strength and throughput where I live (i.e.: crowded/congested wireless networks in an apartment complex).
Did OpenWRT team managed to work around them, or did the manufacturers started to play nicer with open drivers with loadable firmware?
good approach, but your security should not depend on your router anyway, you should be immune to attacks from it
Not exposing your management interface to internet and running a guest network which doesn't have access to said management interfaces can block 95%+ of the attacks, I believe.
yes, defense in depth
The article doesn't disclose the value of "sys.rzadmin.password", but this writeup from 2022 does:
https://boschko.ca/tenda_ac1200_router/
Spoiler: it's "rzadmin". And it looks like there are a bunch of other goodies in the firmware, too.
At that point it’s not even a back door it’s just stupid default root password kind of design which used to be standard in this kind of hardware. Backdoor would at least try to be subtle :)
Backdoors are often (almost always?) designed to look like incompetence so that there's plausible deniability.
That backdoor is so up front about it. We might as well call it a frontdoor.
I mean, it's 99% sure this was supposed to be a debug feature...
and "accidentally" they forgot to disable it when releasing
Sounds like a convenience feature for a dev that they forgot to remove before distribution, since it's this poorly hidden.
In computer security, never attribute to ignorance that which is adequately explained by malice.
You’ve got the saying backwards:
“Never attribute to malice that which is adequately explained by stupidity.”
https://en.wikipedia.org/wiki/Hanlon%27s_razor
Pretty sure the point was to invert it. :)
Yes, I got their point. My point is that’s the opposite of reality.
Maybe it's time to take a closer look at reality and correct this meme, which might casually blur the issue and deflect responsibility?
Looking at the IT security landscape we see every layer, every product category if not every product itself riddled with issues at one point or another. At the same time the incentives to put those security issues in are huge, and we know attackers work systematic, creative and persistent to introduce those weak points.
Security is hard and many bugs certainly happen due to mistakes, but I wouldn't assume that all of those security mishaps stem from an endless series of blunders from "stupid" programmers.
So I would go with “Never attribute to ignorance that which is adequately explained by malice.”
> I wouldn't assume that all of those security mishaps stem from an endless series of blunders from "stupid" programmers.
The saying doesn’t mean that all vulnerabilities are blunders. It means we shouldn’t automatically assume vulnerabilities are nefarious.
If closer inspection proves beyond reasonable doubt that it was placed there deliberately and maliciously then that’s different.
But the point is most vulnerabilities are blunders so it’s better to assume that until proven otherwise.
His point is that in security, the opposite applies. The supposed "incompetence" is just plausible deniability for a malicious act.
Yes, and my point is that hasn’t been the case in my experience.
Looks like this time you interpreted the message in a malicious way.
How? Neither their comment nor mine have anything malicious in their tone nor content.
> Tenda is a supplier of home and business network devices such as routers, switches, wireless access points, and video surveillance equipment.
I was unfamiliar with Tenda.
> Shenzhen Tenda Technology Co.,Ltd. ( https://www.tendacn.com/us/profile )
Tenda may just rebrand, right? It seems like many chinese brands will either rebrand or have a 'competing' brand with the same internals but different externals. (I have no idea if Tenda does this, I've just seen it previously. Specifically with security cameras)
I wish the authors provided some method for checking this vulnerability other than fw version. It seems like Tenda could just change the password and say "yep! all safe now"
Tenda has been around for quite a few years now. I don't imagine they'll rebrand.
I have an ethernet over power adapter somewhere in a cupboard from perhaps 10 years ago.
Back then it was standard for the admin password to be 'admin'. They'd often even print it on the device itself.
> the admin password to be 'admin'. They'd often even print it on the device itself.
Yes but aren't you supposed to change that one? The problem with the rzadmin is that it will continue to work even after you change the regular admin one...
I am still using their Powerline adapters and FWIW they have been very reliable.
Tenda is very popular in Asia, several ISPs use them as their default routers.
It is probably just a brand, like many others, and based on a reference design from the OEM.
I have a small Tenda 5-port gigabit dumb switch. It uses the same switch chip as this TP-Link, just with different branding; even the "SG105" model number is the same:
https://goughlui.com/2022/02/27/unbox-teardown-tp-link-tl-sg...
I’m in the USA and have a Tenda WiFi usb stick. Not as popular as other brands but they are around
The consistency with which networking hardware companies produce such garbage is crazy.
And it’s always amateur hour backdoors somehow. If it was something sophisticated they might get a pass on „ok some security agency made them do it probably“
Or the amateur hour backdoors are those that are found.
Or the amateur hour backdoors are there to be found.
this is definitely a backdoor, not necessarily that they use it to infiltrate users but definitely they put them at risk.
reminds me of a bug I found in some tplink router it compared passwords of 3 different users but that table was empty so basically 15 NULL bytes would log you in as admin lol
Have used their travel wifi product back when hotel wifi was a strange beast. Wouldn't expect to need it now eSIM and ubiquitous internet travel pricing means the hotel wifi may be the LEAST valid path to access things.
I have a free give-away mikrotik unit in the same price bracket (literally free: they were both conference give-aways) it's physically smaller and it runs what appears to be their mainline code. Say what you like about microtik for quality, they provide pretty much every knob and frob you could want.
I’m working on a hotel right now. And I’ve gone to great lengths to make the wifi more secure. Everyone on their own VLAN. Separate PPSK for each room. Credentials are randomly generated and not some ridiculous pattern of last name and room number or similar. We built our own custom access control system, with what at the time was the strongest keycards we could find (mifare desfire ev3), I’m really trying to make a hotel who’s security isn’t such a joke.
How do you distribute credentials to residents?
My Macbook is permanently locked out of Cox's hotspot system (used in some U.S. hotels) because the password was given to me on a tiny label which I couldn't read as a blind person except through OCR, and the OCR was wrong a few too many times.
Do macs not spoof their macid (heh) everytime they join a network? I thought android (and windows?) did that already?
They do, by default. You have to override it on a per-network basis to disable this behavior.
As long as I can bind more than one device in my room, and as long as I can "see" the devices amongst themselves, I'd love this. I can imagine people who want inter-room access but they can live through proxies offsite. If I want to do in room sharing, I need in room wifi.
Gets hard when you bring "smart" TV's to the table. They're going to need to expose into this system somewhat 'credential-free' but if you do it off MAC address then a determined user could disconnect, find MAC, clone ...
It would still be wiser to tie your own router into the hotel system as a gateway, and keep your own PAN behind that.
I stayed at a clinic once, and all the smart TVs were on the same network.. I wonder what would've happened if I streamed a video from my phone to another room's TV.
A quick search reveals several other serious vulnerabilities in Tenda routers that could grant administrator privileges. Therefore, I tend to believe this is due to the company's incompetence and lack of technical skill rather than malicious intent—but it's still a reason to avoid using Tenda products. There's a reason why Tenda's market share is far lower than TP-Link's.
And this is why I handroll my own routers/firewalls, using commodity hardware and a Linux distribution.
Man, I remember doing this in the late 90s with ipchains as the only way to get a router that didn't cost an arm and a leg. Eventually consumer/prosumer routers came out.
What's old is new again.
Tenda has good support among OpenWRT.
So the next step is a hardware or boot firmware backdoor?
(Good to know it remains useful by using openWRT and doesn't become landfill)
Looking to do this to get off stock isp leased router. What's your hardware/distro rec?
Ryzen 5 with a dual 10Gbps NIC, running Debian. Overkill for a router/firewall, but I run other services on the same hardware including an email stack, Podman containers, and small AI model for use within Home Assistant.
I wouldn't buy new hardware. Any modest machine built in the last decade would do. If possible, get a machine with an internal ATX power supply rather than an external brick, they tend to be more reliable.
If all you need is 1Gpbs and WiFi, OpenWrt on consumer hardware is probably enough though.
I have a Lenovo thin client running Debian as internet gateway/firewall. With some minor modifications and a small low power blower fan you can add a dual sfp pcie card in it (not all versions can, though there are more manufacturers of thin clients with 4x pcie slots). The blower fan is because the main fan stops often and it needs some cooling.
Use openWrt (https://openwrt.org), and use their hardware list to pick a consumer router with the feature set you need that can be flashed to use openWrt.
It looks like recent Tenda hardware/firmware is encrypted per below examples, making it harder to audit.
binwalk US_AC10V6.0si_V16.03.62.09_multi_TDE01.bin
binwalk US_BE12ProV1.0mt_V16.03.66.23_TD01.bin The third attempt I tried was unencrypted, and possibly reveals the problem exists on another model this CVE doesn't list as affected:binwalk US_W18EV2_kf_V16.01.0.20\(4766\)_HighPower\ \(1\).bin
Inside is /squashfs-root/webroot_ro/default_ac.cfg which offers: And /squashfs-root/webroot_ro/default_router.cfg which offers: From what I can see quickly (I haven't looked hard), "sys.rzadmin.password" is only referenced from the login() function of /bin/httpd in the context of retrieving a value. This value is retrieved and compared before the error message "login err: password is wrong." is emitted. I can't find any other reference to code in any part of the firmware that may allow a user to change the default value of "sys.rzadmin.password".Also for fun there is a function imsd_upload_log_v1 in /bin/imsd that collects SSIDs, MACs, IP addresses, sys.admin.username, sys.rzadmin.username, timezone, and another function imsd_remote_pwd_get in /bin/imsd that retrieves sys.admin.password. Related library /lib/lubucapi.so also looks like a fun binary to inspect more closely as it contains a command set that seemingly allows either cloud management of Tenda routers and/or remote debugging, and possibly is why imsd_remote_pwd_get exists in /bin/imsd
Common situation for small-company software...
Backdoor passwords left for convenient debugging are not surprising anymore.
My ifconfig is simple: if it's made in Shenzhen, throw it out
I bet more than half of components in all your electronics are made in Shenzhen
Yikes
The US/Israel would never do such a thing, buy UniFi/Fortinet/Palo Alto!
There was a meme going round of a network diagram that layers a Chinese firewall behind a US firewall behind a Russian firewall so they can all block each other countries backdoors.
https://en.wikipedia.org/wiki/Swiss_cheese_model
They'll have a lot of work to do, if they want to catch up with the amount and rate of "hidden authentication backdoors" all those companies (and also Cisco) have. E.g. https://www.thestack.technology/cisco-hard-coding-passwords-...
Not sure if you're joking, but both have already done so. And any US company is subject to secret orders forcing them to implement a backdoor if demanded.
So will this finally be treated as sabotage/criminal hacking, or is it just yet another example of letting manufacturers do whatever they want to their customers without any punishment? Meanwhile if I find and publish the emails of Tenda customers that they accidentally left unprotected, I get raided by the FBI.
Not to sound too alarming. But
Security holes in networking equipment
Affects not just the compromised devices.
Up and out the back door, any 'ol time.
I've seen it last night, and I was like wtf?! Frankly, if they tried to build in some backdoor, I bet they would have done it differently, not so obviously. This must have been some sort of stupidity done for testing purposes, and just got buried deep in the code and forgotten.
This is the main reason why you should always use OpenWRT or other opensource router OS. If it gets an issue, at least it would get patched in the next update.
Yet another Chinese company selling backdoor'd product. Surprise surprise...
Are you referring to the concept of “prayer?”
Almost all consumer electronics come with backdoors—especially given the prevalence of computational advertising. Before criticizing Tenda, we ought to clarify whether this is a consumer-facing (2C) or business-facing (2B) product.