Insufficient verification of data authenticity in Go programming language - CVE-2026-56864
Published: August 18, 2026
Vulnerability identifier: #VU144175
CSH Severity: Medium
CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-56864
CWE-ID: CWE-345
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to serve malicious module content to clients.
The vulnerability exists due to improper verification in cmd/go and golang.org/x/mod/sumdb when validating module content from a GOSUMDB and coordinating GOPROXY. A remote attacker can operate a malicious GOSUMDB with a coordinating GOPROXY to serve malicious module content to clients.
Exploitation requires control of both the checksum database and a coordinating module proxy.
Affected software
Go programming language
How to mitigate CVE-2026-56864
Install security update from vendor's website.
Go programming language - addressed in versions 1.25.13, 1.26.6, 1.27.0 rc.3