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.
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
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| 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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