CVE-2024-7589: OpenSSH pre-authentication async signal safety issue

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-08-12 · updated 2026-06-17
Weakness: CWE-362

Description

A signal handler in sshd(8) may call a logging function that is not async-signal-safe. The signal handler is invoked when a client does not authenticate within the LoginGraceTime seconds (120 by default). This signal handler executes in the context of the sshd(8)'s privileged code, which is not sandboxed and runs with full root privileges. This issue is another instance of the problem in CVE-2024-6387 addressed by FreeBSD-SA-24:04.openssh. The faulty code in this case is from the integration of blacklistd in OpenSSH in FreeBSD. As a result of calling functions that are not async-signal-safe in the privileged sshd(8) context, a race condition exists that a determined attacker may be able to exploit to allow an unauthenticated remote code execution as root.

Affected products

FreeBSD: before 13.0; from 13.1 before 13.3; 13.3-p1, 13.3-p2, 13.3-p3, 13.3-p4, 14.0-beta5, 14.0-p1 (+11) — fixed in 13.0, 13.3

How to fix

Upgrade to a fixed version: FreeBSD 13.0, 13.3. Check the vendor advisory for mitigations.

References

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