Hi Alexander, How did your team find this vulnerability? Manual auditing? Different tool? A formal verification project?
For others looking this up, it's actually SSHamble (without the "s"): Thanks for the correction :)
Best regards,
Fabian Bäumer
M. Sc. Fabian Bäumer
Chair for Network and Data Security Ruhr University Bochum Universitätsstr. 150, Building MC 4/145 44780 Bochum Germany
Am 19.04.2025 um 01:20 schrieb Solar Designer: Hi Fabian,
Thank you very much for this discovery and for the additional detail.
On Fri, Apr 18, 2025 at 02:01:44PM +0200, Fabian Bäumer wrote: Now, what prevented detection of this vulnerability by tools like SSHambles, is that the server does not respond to these requests. For others looking this up, it's actually SSHamble (without the "s"):
https://www.runzero.com/sshamble/ https://github.com/runZeroInc/sshamble
How did your team find this vulnerability? Manual auditing? Different tool? A formal verification project? Am I affected?
All users running an SSH server based on the Erlang/OTP SSH library are likely to be affected by this vulnerability. If your application uses Erlang/OTP SSH to provide remote access, assume you are affected. This has some additional detail on Elixir/Phoenix:
https://paraxial.io/blog/erlang-ssh
"The default configuration for Phoenix does not expose the Erlang SSH daemon to the public internet. It is technically possible you are vulnerable if your application does expose Erlang's SSH daemon, for example Elixir sftp clients do this."
Regarding Matt Keeley's exploit I posted yesterday, they now have a blog post explaining how the exploit was created mostly by AI:
https://platformsecurity.com/blog/CVE-2025-32433-poc
That's very impressive, although it might have been helped by the fix containing a regression test, which already was almost a public PoC:
https://github.com/erlang/otp/commit/6eef04130afc8b0ccb63c9a0d8650209cf54892f#diff-156a6329570e311c82b40c32d19acb37ef6d03339219ea18cd2a2a4e5649c8e5R390
as it included the main steps:
earlyrce(Config) -> [...] {send, hello}, {send, sshmsgkexinit}, {match, #sshmsgkexinit{=''}, receivemsg}, {send, SshMsgChannelOpen}, {send, SshMsgChannelRequest},
Alexander