CVE-2026-56123
It was discovered that socat incorrectly handled the SOCKS5 proxy server reply parser. A remote attacker could possibly use this issue to execute arbitrary code. (CVE-2026-56123) It was discovered that socat incorrectly handled a sample script. A local attacker could possibly use this issue to overwrite arbitrary files. This issue only affected Ubuntu 24.04 LTS. (CVE-2024-54661)
CSIRTS triage
- 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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Exploitation outlook
- Low exploitation risk0.55% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 43% of all EPSS-scored CVEs.
Advisory coverage (2)
- unknownUSN-8511-1: socat vulnerabilitiesubuntu · 2026-07-06
- highCVE-2026-56123: socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parsermsrc · 2026-06-09
External references
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[](https://www.csirts.com/cve/CVE-2026-56123)