OpenSSH client: use-after-free when a server changes its host key during re-exchange

CVSS 9.4CVE-2026-60002Kernel, userspace & hypervisorcurated

Impact

A server that swaps its host key during key re-exchange triggers a use-after-free in the ssh client. The flaw is client-side only, so it does not expose sshd on a GPU node; what it exposes is everything that runs ssh outbound - jump hosts, bastions, Ansible and Slurm prolog scripts, CI runners, fleet-wide orchestration loops. Those clients typically hold agent-forwarded keys and cluster credentials, so an operator-controlled or hijacked destination becomes a path into the management tooling. The record does not demonstrate code execution, only the use-after-free, and reaching it requires the client to connect to a server the attacker controls or can impersonate.

Who can reach it

A malicious or compromised SSH server (or an on-path attacker able to act as one) against a client that connects to it. No authentication needed - the condition occurs during key exchange, before the client authenticates the server's new key.

What to do

Update OpenSSH to 10.4/10.4p1 or your distribution's backport across anything that runs ssh outbound - bastions, controllers, CI images, node images baked for the fleet. No daemon restart is needed for the client path and no node reboot; existing long-lived ssh sessions keep using the old binary, so re-launch automation loops after updating.

References

https://nvd.nist.gov/vuln/detail/CVE-2026-60002 https://www.openssh.com/releasenotes.html#10.4p1 https://www.openwall.com/lists/oss-security/2026/07/06/5 https://marc.info/?l=openssh-unix-dev&m=178333966933090&w=2

This entry is curated: imported from vendor advisories with machine assistance, not yet individually verified. Confirm against your vendor's advisory before acting, and report anything wrong.