CVE-2026-56123 Details
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.
A heap-based buffer overflow vulnerability has been identified in socat versions 1.8.0.0 prior to 1.8.1.2. This vulnerability 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, leading to a negative bytes_to_read value. This value is then implicitly converted to size_t, causing an unbounded heap write into the 262-byte reply buffer with attacker-controlled size and content.
Users can upgrade to socat version 1.8.1.2 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 26, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser | [email protected] | Third Party Advisory |
| http://www.dest-unreach.org/socat/CHANGES | [email protected] | Release Notes |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-122 | Heap-based Buffer Overflow | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| dest-unreach socat | >= 1.8.0.0, < 1.8.1.2 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 26, 2026 | Initial Analysis | [email protected] |
| Jun 26, 2026 | CVE Modified | CISA-ADP |
| Jun 25, 2026 | New CVE Received | [email protected] |