CVE-2024-6387
8.14.20%
CVE-2024-6387: regreSSHion - Time is a Flat Circle (of Root Shells)
Amit Schendel
Senior Security ResearcherJan 3, 2026·5 min read·7 visits
PoC AvailableCISA KEV Listed
Executive Summary (TL;DR)
OpenSSH's sshd calls unsafe functions (syslog) inside a signal handler. By winning a precise race condition, an attacker can corrupt the heap and gain unauthenticated root access. It takes about 6-8 hours of continuous attempts to exploit, but the result is a full system compromise.
A signal handler race condition in OpenSSH's server (sshd) allows unauthenticated remote attackers to achieve root code execution on glibc-based Linux systems. This is a regression of CVE-2006-5051, proving that code history repeats itself if you don't write regression tests.
Official Patches
Fix Analysis (1)
Technical Appendix
CVSS Score
8.1/ 10
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:HEPSS Probability
4.20%
Top 15% most exploited
14,000,000
Estimated exposed hosts via Shodan
Affected Systems
OpenSSH servers running on glibc-based Linux systemsVersions 8.5p1 through 9.7p1
Affected Versions Detail
| Product | Affected Versions | Fixed Version |
|---|---|---|
OpenSSH OpenBSD | >= 8.5p1, < 9.8p1 | 9.8p1 |
| Attribute | Detail |
|---|---|
| Attack Vector | Network (Port 22) |
| Complexity | High (Race Condition) |
| Privileges | None (Unauthenticated) |
| CVSS v3.1 | 8.1 (High) |
| CWE | CWE-364: Signal Handler Race Condition |
| Exploit Status | Proof of Concept Available |
MITRE ATT&CK Mapping
CWE-364
Signal Handler Race Condition
The software executes a signal handler that calls a non-reentrant function, leading to undefined behavior or memory corruption.
Known Exploits & Detection
Vulnerability Timeline
Vulnerability Disclosed by Qualys
2024-07-01
OpenSSH 9.8p1 Released
2024-07-01
Added to CISA KEV
2024-07-08