Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Dest-Unreach | Socat | >= 1.8.0.0, < 1.8.1.2 |
Related Weaknesses (CWE)
References
- http://www.dest-unreach.org/socat/CHANGESRelease Notes
- https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-replyThird Party Advisory
FAQ
What is CVE-2026-56123?
CVE-2026-56123 is a vulnerability with a CVSS score of 8.1 (HIGH). 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 f...
How severe is CVE-2026-56123?
CVE-2026-56123 has been rated HIGH with a CVSS base score of 8.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-56123?
Check the references section above for vendor advisories and patch information. Affected products include: Dest-Unreach Socat.