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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-56123

38
FAUCET Score

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.

First published: Jun 25, 2026Last modified: Jun 25, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 1.8.0.0, < 1.8.1.2CPE matchmatch criteria
cpe:2.3:a:dest-unreach:socat:*:*:*:*:*:*:*:*
>= 1.8.0.0, < 1.8.1.2CPE match
cpe:2.3:a:socat:socat:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 4.0

9.2CRITICAL

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
VS Confidentiality
HIGH
VS Integrity
HIGH
VS Availability
HIGH
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.31%
Probability of exploitation in next 30 days
EPSS Percentile
23.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0031 is in the 3rd percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

ubuntupatch availablevia ubuntu_usn
Product: socat (noble)Fixed in: 1.8.0.0-4ubuntu0.1
ubuntupatch availablevia ubuntu_usn
Product: socat (resolute)Fixed in: 1.8.1.1-1ubuntu0.1

Vendor Advisories (2)

ubuntuUSN-8511-1

socat vulnerabilities

Jul 6, 2026
microsoft2026-Jun/CVE-2026-56123Critical

socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser

Jun 9, 2026

References

vulncheck.com / advisories/socat-heap-buffer-overflow-via-socks5-reply-parser
Third Party Advisory
dest-unreach.org / socat/CHANGES
Release Notes