🛡️ CVE-2026-56123 on Alpine — socat

⚪ Unknown ✅ No Known Exploit OSV

N/A

CVSS Score

0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2026-56123 as tracked by Alpine, for the package socat. The fix is available in version 1.8.1.2-r0; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, 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 high, integrity high, availability high.

Weakness class

ALPINE-CVE-2026-56123 is classified as CWE-122: Heap-based Buffer Overflow. A write past the end of a heap allocation corrupts allocator metadata or neighbouring objects.

Affected software

ALPINE-CVE-2026-56123 is recorded against 1 package.

socat (from 1.8.0.0 up to 1.8.1.2-r0)

Timeline and source

Published on 25 June 2026 and last revised on 8 July 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security.alpinelinux.org (Advisory)

Details

Severity Unknown

CVSS Score N/A

CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE N/A

Public Exploit ✅ No

Source OSV

Published 2026-06-25

Updated 2026-08-11

Modified 2026-07-08

Fix URL N/A

Affected Packages

Software	From version	Fixed in
socat	1.8.0.0	1.8.1.2-r0

References

ADVISORY https://security.alpinelinux.org/vuln/CVE-2026-56123

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