update: openssh

[dongsupark]

Name: openssh
CVEs: CVE-2025-26465, CVE-2025-26466
CVSSs: n/a, n/a (probably medium)
Action Needed: update to >= 9.9_p2

Summary:

• CVE-2025-26465: The OpenSSH client is vulnerable to an active machine-in-the-middle attack if the VerifyHostKeyDNS option is enabled (it is disabled by default): when a vulnerable client connects to a server, an active machine-in-the-middle can impersonate the server by completely bypassing the client's checks of the server's identity.
  • https://bugzilla.redhat.com/show_bug.cgi?id=2344780
• CVE-2025-26466: A flaw was found in the OpenSSH package. For each ping packet the SSH server receives, a pong packet is allocated in a memory buffer and stored in a queue of packages. It is only freed when the server/client key exchange has finished. A malicious client may keep sending such packages, leading to an uncontrolled increase in memory consumption on the server side. Consequently, the server may become unavailable, resulting in a denial of service attack.
  • https://bugzilla.redhat.com/show_bug.cgi?id=2345043

See also https://seclists.org/oss-sec/2025/q1/144.

refmap.gentoo: https://bugs.gentoo.org/949904

[tmsdce]

Hi @dongsupark

I see that a new version of Flatcar stable (4152.2.1) was just released. It mentions that the two CVEs has been fixed but the version of openssh shipped with the new release is not 9.9_p2 (which fixes the CVEs) but 9.8_p1-r4. This is confirmed by the version shown in one of my node running stable

# ssh -V
OpenSSH_9.8p1, OpenSSL 3.2.3 3 Sep 2024

This is quite confusing. Are the two CVEs actually patched ?

[t-lo]

Hello @tmsdce , thank you for bringing this up. For security releases we only include the absolute minimum of changes necessary to address the issue. This ensures a low-risk release (no build or test breakage which would delay the release) as well as a low-risk upgrade (i.e. no side effects in production) for our users. Therefore, we did not upgrade to a new OpenSSH release that might ship unrelated changes; instead, we just applied patches for the security issues (signified by the package release version bump; -r3 -> -r4. The CVEs are patched.

[tmsdce]

Thanks for your reply @t-lo
This makes sense 👍