Unauthenticated code execution via SIGALRM cleanup race
Published Jul 8, 2024 · Updated Aug 21, 2026
Signal-handler race in Red Hat's RHEL 9 OpenSSH build allows remote attackers to execute code as the unprivileged sshd user. The sshd cleanup_exit() path handles an asynchronous SIGALRM by calling functions such as syslog() that are not async-signal-safe, permitting state corruption during unauthenticated connection cleanup. Exploitation requires winning a high-complexity race after LoginGraceTime expires; resulting code remains confined to sshd's unprivileged child.
Summary
What happened
Signal-handler race in Red Hat's RHEL 9 OpenSSH build allows remote attackers to execute code as the unprivileged sshd user. The sshd cleanup_exit() path handles an asynchronous SIGALRM by calling functions such as syslog() that are not async-signal-safe, permitting state corruption during unauthenticated connection cleanup. Exploitation requires winning a high-complexity race after LoginGraceTime expires; resulting code remains confined to sshd's unprivileged child.
The record
- CVE
- CVE-2024-6409
- Published
- Jul 8, 2024
- Updated
- Aug 21, 2026
- Vendor
- Red Hat
- Product
- Red Hat OpenShift Container Platform 4.14
- Classifications
- CWE-364, T1210
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 8, 2024CVE publishedPublication date reported by the CVE source.
- Aug 21, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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