CVE-2025-8277

Publication date 9 September 2025

Last updated 23 February 2026

Ubuntu priority

Cvss 3 Severity Score

Description

A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.

Read the notes from the security team

Why is this CVE low priority?

libssh developers consider this to be a low severity issue

Learn more about Ubuntu priority

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libssh	25.10 questing	Fixed 0.11.2-1ubuntu0.2
	25.04 plucky	Ignored end of life, was needs-triage
	24.04 LTS noble	Fixed 0.10.6-2ubuntu0.3
	22.04 LTS jammy	Fixed 0.9.6-2ubuntu0.22.04.6
	20.04 LTS focal	Fixed 0.9.3-2ubuntu2.5+esm3
	18.04 LTS bionic	Fixed 0.8.0~20170825.94fa1e38-1ubuntu0.7+esm6
	16.04 LTS xenial	Not affected

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Notes

mdeslaur

This does not affect servers, only clients and is only a memory leak that may eventually lead to a crash.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
libssh	Upstream: ?h=stab Upstream: ?h=stab Upstream: ?h=stab Upstream: ?h=stab

Severity score breakdown

Parameter	Value
Base score	3.1 · Low
Attack vector	Network
Attack complexity	High
Privileges required	Low
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	Low
Vector	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L