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 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 v3 8.1 HIGH

8.1^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.2 / Impact : 5.9

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
http://www.dest-unreach.org/socat/CHANGES	Release Notes
https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser	Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:dest-unreach:socat:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-06-25 17:17

Updated : 2026-06-26 16:50

NVD link : CVE-2026-56123

Mitre link : CVE-2026-56123

CVE.ORG link : CVE-2026-56123

JSON object : View

Products Affected

dest-unreach

socat

CWE

CWE-122

Heap-based Buffer Overflow

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