CVE-2026-56123

socat: socat versions 1.8.0.0 through 1.8.1.1 contain a heap-based buffer overflow vulnerability that allows a malicious SOC...

CVE-2026-56123 is fixed in 3 products on 1 platform, first by socat 1.8.1.1-1ubuntu0.1, released June 25, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

Urgent
CVSS
9.8
critical
Exploitation
None reported
No vendor assessment
CISA KEV
Not listed
Not in the Known Exploited Vulnerabilities catalog
EPSS
0.0031
24th percentile

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.

Where it's fixed

ProductFixed inFixReleased
Linux
socat · Debian 13.5 (trixie) 1.8.0.3-1+deb13u1 DEBIAN-CVE-2026-56123 Jul 3, 2026
socat · Debian 14 1.8.1.3-1 DEBIAN-CVE-2026-56123 Jul 3, 2026
socat · Fedora 43 1.8.1.3-1.fc43 FEDORA-2026-232FFC1325 Oct 7, 2026
socat · Ubuntu 24.04.5 LTS (noble) 1.8.0.0-4ubuntu0.1 socat 1.8.0.0-4ubuntu0.1 Jul 7, 2026
socat · Ubuntu 26.04.1 LTS (resolute) 1.8.1.1-1ubuntu0.1 socat 1.8.1.1-1ubuntu0.1 Jun 25, 2026
socat-debuginfo · Fedora 43 1.8.1.3-1.fc43 FEDORA-2026-232FFC1325 Oct 7, 2026
socat-debugsource · Fedora 43 1.8.1.3-1.fc43 FEDORA-2026-232FFC1325 Oct 7, 2026

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