Root code execution via unsafe SIGALRM handler
Published Jul 1, 2024 · Updated Sep 1, 2026
Signal handler race condition in OpenSSH 8.5p1 through 9.7p1 allows remote attackers to execute code as root through unauthenticated SSH connections. After LoginGraceTime expires, sshd's SIGALRM handler invokes async-signal-unsafe functions such as syslog(), enabling heap corruption during interrupted glibc calls. Exploitation requires a non-OpenBSD, glibc-based system with LoginGraceTime enabled and repeated timing attempts; successful execution has root privileges.
Summary
What happened
Signal handler race condition in OpenSSH 8.5p1 through 9.7p1 allows remote attackers to execute code as root through unauthenticated SSH connections. After LoginGraceTime expires, sshd's SIGALRM handler invokes async-signal-unsafe functions such as syslog(), enabling heap corruption during interrupted glibc calls. Exploitation requires a non-OpenBSD, glibc-based system with LoginGraceTime enabled and repeated timing attempts; successful execution has root privileges.
The record
- CVE
- CVE-2024-6387
- Published
- Jul 1, 2024
- Updated
- Sep 1, 2026
- Vendor
- Siemens
- Product
- SINAMICS IIoT module
- Classifications
- CWE-362, CWE-364, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 1, 2024CVE publishedPublication date reported by the CVE source.
- Sep 1, 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <V1.0 HF1
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
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Karmakstylez CVE-2024-6387 32-bit exploitfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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