Insufficient verification of data authenticity in Go programming language - CVE-2026-56865
Published: August 18, 2026
Vulnerability identifier: #VU144176
CSH Severity: High
CVSS v4: 8.8 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-56865
CWE-ID: CWE-345
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass integrity verification and persist attacker-controlled module content in the local Go module cache.
The vulnerability exists due to improper verification of sumdb tiles in cmd/go and golang.org/x/mod/sumdb/tlog when processing responses from a GOPROXY. A remote attacker can serve forged sumdb tiles and malicious module content to bypass integrity verification and persist attacker-controlled module content in the local Go module cache.
This issue requires use of a malicious GOPROXY.
Affected software
Go programming language
How to mitigate CVE-2026-56865
Install security update from vendor's website.
Go programming language - addressed in versions 1.25.13, 1.26.6, 1.27.0 rc.3