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🛡️ CVE-2023-25136 on Ubuntu — openssh

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

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."

Distribution advisory

This page covers CVE-2023-25136 as tracked by Ubuntu, for the package openssh. No fixed version has been recorded for this distribution yet.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity low, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: Low — limited, and the attacker does not choose what is affected.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

UBUNTU-CVE-2023-25136 is classified as CWE-415: Double Free. The same allocation is released twice, corrupting allocator bookkeeping.

Affected software

UBUNTU-CVE-2023-25136 is recorded against 1 package.

  • openssh

Timeline and source

Published on 3 February 2023 and last revised on 30 October 2025. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

ubuntu.com (Report)
www.openwall.com (Report)
www.openwall.com (Report)
jfrog.com (Report)
www.cve.org (Report)

Other advisories for this package

openssh has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-415: Double Free) in other software:

CVE-2023-25136 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2023-02-03
Updated 2026-08-20
Modified 2025-10-30
Fix URL N/A

Affected Packages

Software From version Fixed in
openssh — —

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