CVE catalog
CVE-2026-56123
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
- Severity
- Critical · CVSS 9.2
- Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.31% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | socat | sid | 1.8.1.3-2 | fixed |
| Debian | socat | forky | 1.8.1.3-2 | fixed |
| Debian | socat | trixie | 1.8.0.3-1+deb13u1 | fixed |
| Debian | socat | bookworm | 1.7.4.4-2 | not affected |
| Cpe | socat | Not reported | 1.8.0.0-4ubuntu0.1 | fixed |
| Cpe | socat | Not reported | Not reported | not affected |
| Cpe | socat | Not reported | 1.8.1.2 | fixed |
| Alpine | socat | 3.21 | 1.8.1.2-r0 | fixed |
| Alpine | socat | 3.22 | 1.8.1.2-r0 | fixed |
| Alpine | socat | 3.23 | 1.8.1.2-r0 | fixed |
| Alpine | socat | 3.24 | 1.8.1.2-r0 | fixed |
| Ubuntu | socat | 24.04 | 1.7.4.4-2 | vulnerable |
| Ubuntu | socat | 24.04 | 1.8.0.0-4 | vulnerable |
| Ubuntu | socat | 24.04 | 1.8.0.0-4build1 | vulnerable |
| Ubuntu | socat | 24.04 | 1.8.0.0-4build2 | vulnerable |
| Ubuntu | socat | 24.04 | 1.8.0.0-4build3 | vulnerable |
| Ubuntu | socat | 24.04 | 1.8.0.0-4ubuntu0.1 | fixed |
| Ubuntu | socat | 25.10 | 1.8.0.2-1 | vulnerable |
| Ubuntu | socat | 25.10 | 1.8.0.3-1 | vulnerable |
| Ubuntu | socat | 25.10 | 1.8.0.3-1build1 | vulnerable |
| Ubuntu | socat | 26.04 | 1.8.0.3-1build1 | vulnerable |
| Ubuntu | socat | 26.04 | 1.8.1.0-1 | vulnerable |
| Ubuntu | socat | 26.04 | 1.8.1.0-2 | vulnerable |
| Ubuntu | socat | 26.04 | 1.8.1.1-1 | vulnerable |
| Ubuntu | socat | 26.04 | 1.8.1.1-1ubuntu0.1 | fixed |
| Opensuse | socat | tumbleweed | 1.8.1.3-1.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | socat | source | sid | 1.8.1.3-1 | not yet assigned | Not reported | Not reported |
| Debian | socat | source | forky | 1.8.1.3-1 | not yet assigned | Not reported | Not reported |
| Debian | socat | source | trixie | 1.8.0.3-1+deb13u1 | not yet assigned | Not reported | Not reported |
| Debian | socat | source | bookworm | Not affected | unimportant | Not reported | Not reported |
| Cpe | socat | cpe | Not reported | 1.8.0.0-4ubuntu0.1 | Not reported | Not reported | Not reported |
| Cpe | socat | cpe | Not reported | 1.8.1.2 | Not reported | Not reported | Not reported |
| Alpine | socat | apk | 3.21 | 1.8.1.2-r0 | Not reported | ALPINE-CVE-2026-56123 | Not reported |
| Alpine | socat | apk | 3.22 | 1.8.1.2-r0 | Not reported | ALPINE-CVE-2026-56123 | Not reported |
| Alpine | socat | apk | 3.23 | 1.8.1.2-r0 | Not reported | ALPINE-CVE-2026-56123 | Not reported |
| Alpine | socat | apk | 3.24 | 1.8.1.2-r0 | Not reported | ALPINE-CVE-2026-56123 | Not reported |
| Ubuntu | socat | deb | 24.04 | 1.8.0.0-4ubuntu0.1 | Not reported | UBUNTU-CVE-2026-56123 | Not reported |
| Ubuntu | socat | deb | 26.04 | 1.8.1.1-1ubuntu0.1 | Not reported | UBUNTU-CVE-2026-56123 | Not reported |
| Opensuse | socat | rpm | tumbleweed | 1.8.1.3-1.1 | Not reported | OPENSUSE-SU-2026:11151-1 | Not reported |
OpenFactory catalog packages
[Debian 13 (Trixie)]
- [socat]Affected
Details (2)
1.8.0.3-1· amd64 · trixieAffected · Fixed:
1.8.0.3-1+deb13u1nvd · socat · debian · 13
1.8.0.3-1· arm64 · trixieAffected · Fixed:
1.8.0.3-1+deb13u1nvd · socat · debian · 13
[openSUSE Tumbleweed]
- [socat-extra]Unknown
Source package: [socat]
Details (1)
1.8.1.3-2.1· x86_64 · tumbleweedUnknown · Fixed:
1.8.1.3-1.1Version impact unknown
nvd · socat · opensuse · tumbleweed
- [socat]Fixed
Source package: [socat]
Details (1)
1.8.1.3-2.1· x86_64 · tumbleweedFixed · Fixed:
1.8.1.3-1.1nvd · socat · opensuse · tumbleweed
[Debian 12 (Bookworm)]
- [socat]Not affected
Details (4)
1.7.4.4-2· amd64 · bookwormNot affected
nvd · socat · debian · bookworm
1.7.4.4-2· arm64 · bookwormNot affected
nvd · socat · debian · bookworm
1.8.0.0-4~bpo12+1· amd64 · bookworm-backportsNot affected
nvd · socat · debian · bookworm
1.8.0.0-4~bpo12+1· arm64 · bookworm-backportsNot affected
nvd · socat · debian · bookworm
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_11151-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-56123]
- [https://osv.dev/vulnerability/ALPINE-CVE-2026-56123]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-56123]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-56123]
- [https://osv.dev/vulnerability/openSUSE-SU-2026:11151-1]
- [https://security-tracker.debian.org/tracker/CVE-2026-56123]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-56123.json]
- [https://ubuntu.com/security/notices/USN-8511-1]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]