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Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

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Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#21

It's pretty interesting that they didn't just introduce an RCE that anyone can exploit, it requires the attacker's private key. It's ironically a very security conscious vulnerability.

For real, it's almost like a state-sponsored exploit. It's crafted and executed incredibly well, the performance issue feels like pure luck it got found.

Yeah, we should probably expect that there are roughly 1/p(found) more of these lurking out there. Not a pleasant thought.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#22
> Note: successful exploitation does not generate any log entries.

Does this mean, had this exploit gone unnoticed, the attacker could have executed arbitrary commands as root without even a single sshd log entry on the compromised host regarding the 'connection'?

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#23

It's pretty interesting that they didn't just introduce an RCE that anyone can exploit, it requires the attacker's private key. It's ironically a very security conscious vulnerability.

For real, it's almost like a state-sponsored exploit. It's crafted and executed incredibly well, the performance issue feels like pure luck it got found.

It'd make total sense if it was. This way you get to have the backdoor without your enemies being able to use it against your own companies.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#24

It's pretty interesting that they didn't just introduce an RCE that anyone can exploit, it requires the attacker's private key. It's ironically a very security conscious vulnerability.

Am I reading it correctly that the payload signature includes the target SSH host key? So you can't just spray it around to servers, it's fairly computationally expensive to send it to a host.

*host key fingerprint, but I assume what you've meant.

It's practically a good backdoor then, crypto graphically protected and safe against "re-play" attacks.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#25
post #7
post #5

Earlier quoted context omitted.

It's a POC nevertheless, it's a complete implementation of the RCE minus obviously the private key.

It doesn't matter. The people with the private key already knew all of this because they implemented it. The script kiddies without the private key can't do anything without it. A POC doesn't help them in any way. A way to check if servers are vulnerable is probably by querying the package manager for the installed version of xz. Not very sophisticated, but it'll work.

Are you saying POCs are pointless unless a script kiddie can use it?

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#26

Imagine how frustrating it has to be for the attacker to meticulously plan and execute this and get foiled so late in the game, and so publicly

Must be punching the air right now

Or...falling back on less noticed contingency plans...

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#27

Imagine how frustrating it has to be for the attacker to meticulously plan and execute this and get foiled so late in the game, and so publicly

Must be punching the air right now

Or, they must be strapped into a chair having teeth being pulled out by whoever directed them.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#28
post #6

Has anyone tried the PoC against one of the anomalous process behavior tools? (Carbon Black, AWS GuardDuty, SysDig, etc.) I’m curious how likely it is that someone would have noticed relatively quickly had this rolled forward and this seems like a perfect test case for that product category.

Sysdig released a blog on friday. "For runtime detection, one way to go about it is to watch for the loading of the malicious library by SSHD. These shared libraries often include the version in their filename."

The blog has the actual rule content which I haven't seen from other security vendors

https://sysdig.com/blog/cve-2024-3094-detecting-the-sshd-bac...

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#29
post #9

Have we seen exploitation in the wild yet?

If it hadn't been discovered for another month or so, then it would have appeared in stable Fedora 40, Ubuntu 24.4 and Debian, and then it definitely would have been exploited. Another year it would have been in RHEL 10. Very luck escape.

Re: Xzbot: Notes, honeypot, and exploit demo for the xz backdoor

#30
Do we know if this exploit only did something if a SSH connection was made? There's a list of strings from it on Github that includes "DISPLAY" and "WAYLAND_DISPLAY":

https://gist.github.com/q3k/af3d93b6a1f399de28fe194add452d01

These don't have any obvious connection to SSH, so maybe it did things even if there was no connection. This could be important to people who ran the code but never exposed their SSH server to the Internet, which some people seem to be assuming was safe.

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