CVE-2023-25136 Memory corruption in n/a

Medium 6.5 Published 3 Feb 2023 Updated 14 Oct 2026

Unauthenticated remote attackers can exploit a double-free in OpenSSH to potentially execute arbitrary code or crash the service.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2023-25136?

CVE-2023-25136 is a medium-severity memory corruption vulnerability in Fedoraproject Fedora, published on 3 Feb 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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."

Weakness: CWE-415

Which versions are affected by CVE-2023-25136?

It affects 6 products.

Linux distribution packages (28)

`openssh` AlmaLinux:9	All versions	`8.7p1-29.el9_2`
`openssh-askpass` AlmaLinux:9	All versions	`8.7p1-29.el9_2`
`openssh-clients` AlmaLinux:9	All versions	`8.7p1-29.el9_2`
`openssh-keycat` AlmaLinux:9	All versions	`8.7p1-29.el9_2`
`openssh-server` AlmaLinux:9	All versions	`8.7p1-29.el9_2`
`pam_ssh_agent_auth` AlmaLinux:9	All versions	`0.10.4-5.29.el9_2`
`openssh-askpass` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-askpass-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-clients-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-debugsource` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-keycat-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-server-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`openssh-sk-dummy-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:8.7p1-29.el9_2`
`pam_ssh_agent_auth` Red Hat:enterprise_linux:9::appstream	All versions	`0:0.10.4-5.29.el9_2`
`pam_ssh_agent_auth-debuginfo` Red Hat:enterprise_linux:9::appstream	All versions	`0:0.10.4-5.29.el9_2`
`openssh` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-askpass-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-clients` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-clients-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-debugsource` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-keycat` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-keycat-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-server` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-server-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`openssh-sk-dummy-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:8.7p1-29.el9_2`
`pam_ssh_agent_auth-debuginfo` Red Hat:enterprise_linux:9::baseos	All versions	`0:0.10.4-5.29.el9_2`

Products include Fedoraproject Fedora, Netapp 500f Firmware, Netapp A250 Firmware, Netapp C250 Firmware, Netapp Ontap Select Deploy Administration Utility, OpenSSH.

How do I fix CVE-2023-25136?

Upgrade to a fixed version.

Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.

Is CVE-2023-25136 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-25136 exists.

Public exploit code: 11 proofs of concept on GitHub.

All Fedoraproject Fedora vulnerabilities

Sources

Also known as ALSA-2023:2645, BELL-CVE-2023-25136, DEBIAN-CVE-2023-25136, GHSA-w62j-g234-3f6f, JLSEC-2026-66, OESA-2023-1063 and 2 more.