CVE-2026-56123

Publication date 25 June 2026

Last updated 6 July 2026

Ubuntu priority

Cvss 3 Severity Score

Description

socat versions 1.8.0.0 through 1.8.1.1 contain a heap-based buffer overflow vulnerability that allows a malicious SOCKS5 proxy server to overwrite adjacent heap memory by exploiting a sign-extension flaw in the DOMAINNAME reply parser. During connection setup, the domain name length byte is read through a signed char field causing a negative bytes_to_read value that is implicitly converted to size_t, resulting in an unbounded heap write into the 262-byte reply buffer with attacker-controlled size and content.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
socat	26.04 LTS resolute	Fixed 1.8.1.1-1ubuntu0.1
	25.10 questing	Needs evaluation
	24.04 LTS noble	Fixed 1.8.0.0-4ubuntu0.1
	22.04 LTS jammy	Not affected
	20.04 LTS focal	Not affected
	18.04 LTS bionic	Not affected
	14.04 LTS trusty	Not affected

Patch details

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

Package	Patch details
socat	Upstream: d44cd1c Upstream: af5388c

Severity score breakdown

CVSS version:

Base score 9.2 · Critical

Base metrics

Parameter	Value
Attack vector	Network
Attack complexity	High
Attack requirements	None
Privileges required	None
User interaction	None
Vulnerable system - Confidentiality impact	High
Vulnerable system - Integrity impact	High
Vulnerable system - Availability impact	High
Subsequent system - Confidentiality impact	None
Subsequent system - Integrity impact	None
Subsequent system - Availability impact	None

Scores

Parameter	Value
Base score	9.2 · Critical
Base + Threat score	-
Base + Environmental score	-
Base + Threat + Environmental score	-

Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Base score 8.1 · High