CVE-2026-56123: socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser

highCVSS 8.1CVE-2026-56123

CSIRTS triage

vendor: socat product: socat Memory corruptionaffected: 1.8.0.0 - 1.8.1.1

What: A heap buffer overflow vulnerability exists in the SOCKS5 Reply Parser.
Who is affected: Deployments of socat versions between 1.8.0.0 and 1.8.1.1.
Urgency: Remediation is urgent due to the high severity and potential for exploitation.
Action: Upgrade socat to a version beyond 1.8.1.1 to mitigate this vulnerability.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 8.1
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56123

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-561230.31% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 23% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-56123	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownUSN-8511-1: socat vulnerabilitiesubuntu

Recent advisories for socat

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

medium[UPDATE] [medium] Red Hat Enterprise Linux (socat): Vulnerability allows file manipulationcert-bund · 2026-07-07
unknownUSN-8511-1: socat vulnerabilitiesubuntu · 2026-07-06