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CVE-2026-56865GO-2026-6179BIT-GOLANG-2026-56865

Fix transparency log tile verification bypass in golang.org/x/mod/sumdb/tlog

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 1.25.13, 1.26.6, 1.27.0-rc.3, 0.40.0
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. This attack allows for a malicious GOPROXY to serve malicious module content that cannot be detected by evaluating the transparency log. All tiles are now correctly verified against their parents. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • cmd/go

    fixed in 1.25.13; From 1.26.0-0 · fixed in 1.26.6; From 1.27.0-0 · fixed in 1.27.0-rc.3

  • golang.org/x/mod/sumdb/tlog

    fixed in 0.40.0

  • toolchainGo

    fixed in 1.25.13; From 1.26.0-0 · fixed in 1.26.6; From 1.27.0-0 · fixed in 1.27.0-rc.3

  • golang.org/x/modGo

    fixed in 0.40.0

References 5

go.dev

groups.google.com

pkg.go.dev