Memory Leak The advisory has been revoked - it doesn't affect any version of package openssh (opens in a new tab)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RHEL9-OPENSSH-12340822
- published1 Sept 2025
- disclosed3 Feb 2023
Introduced: 3 Feb 2023
CVE-2023-25136 (opens in a new tab)Amendment
The Red Hat security team deemed this advisory irrelevant for RHEL:9.
NVD Description
Note: Versions mentioned in the description apply only to the upstream openssh package and not the openssh package as distributed by RHEL.
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."
References
- https://access.redhat.com/security/cve/CVE-2023-25136
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JGAUIXJ3TEKCRKVWFQ6GDAGQFTIIGQQP/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/R7LKQDFZWKYHQ65TBSH2X2HJQ4V2THS3/
- 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://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
- https://github.com/Christbowel/CVE-2023-25136