Description
A certain Debian patch for OpenSSH before 4.3p2-9etch3 on etch; before 4.6p1-1 on sid and lenny; and on other distributions such as SUSE uses functions that are not async-signal-safe in the signal handler for login timeouts, which allows remote attackers to cause a denial of service (connection slot exhaustion) via multiple login attempts. NOTE: this issue exists because of an incorrect fix for CVE-2006-5051.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | openssh | 1:4.6p1-1 | — |
| Debian 13 | openssh | 1:4.6p1-1 | — |
| Debian 12 | openssh | 1:4.6p1-1 | — |
| Debian 4.0 | openssh | 1:4.3p2-9etch3 | DSA-1638-1 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
GitHub 1 repository
-
bigb0x/CVE-2024-6387 ★ 35 · Jul 1, 2024
Bulk Scanning Tool for OpenSSH CVE-2024-6387, CVE-2006-5051 , CVE-2008-4109 and others.
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 1
- DSA-1638-1 openssh - denial of service Debian Security (DSA / DLA) · Mar 9, 2026
References
- USN-649-1 vendor-advisory
- openssh-signalhandler-dos(45202) vdb-entry
- 31885 third-party-advisory
- 1020891 vdb-entry
- DSA-1638 vendor-advisory
- SUSE-SR:2008:020 vendor-advisory
- 32080 third-party-advisory
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=498678
- 32181 third-party-advisory
- [oss-security] 20240701 CVE-2024-6387: RCE in OpenSSH's server, on glibc-based Linux systems mailing-list