CVE-2023-25136
Published: October 18, 2023Last modified: July 22, 2025
Description
OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. This is fixed in OpenSSH 9.2. The double free can be leveraged, by an unauthenticated remote attacker in the default configuration, to jump to any location in the sshd address space. One third-party report states "remote code execution is theoretically possible."
Severity score breakdown
| Parameter | Value |
|---|---|
| Base score | 6.5 |
| Attack Vector | NETWORK |
| Attack complexity | HIGH |
| Privileges required | NONE |
| User interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality | NONE |
| Integrity impact | LOW |
| Availability impact | HIGH |
| Vector | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H |
Status
| Product | Release | Package | Status |
|---|---|---|---|
| Alpaquita Linux | 23 LTS | openssh | Fixed (9.1_p1-r7) |
| Stream | openssh | Not affected (9.4_p1-r0) | |
| Hardened Containers | 23 LTS | openssh | Fixed (9.1_p1-r7) |
| Stream | openssh | Not affected (9.4_p1-r0) |
References
- http://www.openwall.com/lists/oss-security/2023/02/13/1
- http://www.openwall.com/lists/oss-security/2023/02/22/1
- http://www.openwall.com/lists/oss-security/2023/02/22/2
- http://www.openwall.com/lists/oss-security/2023/02/23/3
- http://www.openwall.com/lists/oss-security/2023/03/06/1
- http://www.openwall.com/lists/oss-security/2023/03/09/2
- https://bugzilla.mindrot.org/show_bug.cgi?id=3522
- https://ftp.openbsd.org/pub/OpenBSD/patches/7.2/common/017_sshd.patch.sig
- https://github.com/openssh/openssh-portable/commit/486c4dc3b83b4b67d663fb0fa62bc24138ec3946
- https://jfrog.com/blog/openssh-pre-auth-double-free-cve-2023-25136-writeup-and-proof-of-concept/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
- https://lists.fedoraproject.org/archives/list/[email protected]/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
- https://lists.fedoraproject.org/archives/list/[email protected]/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
- https://news.ycombinator.com/item?id=34711565
- https://security.gentoo.org/glsa/202307-01
- https://security.netapp.com/advisory/ntap-20230309-0003/
- https://www.openwall.com/lists/oss-security/2023/02/02/2