CVE-2026-56865 (GCVE-0-2026-56865)
Vulnerability from cvelistv5 – Published: 2026-08-13 21:58 – Updated: 2026-08-14 15:34
VLAI
EPSS
VEX
Title
Fix transparency log tile verification bypass in golang.org/x/mod/sumdb/tlog
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
Severity
8.4 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-14 15:33 UTC
CWE
- CWE-347 - Improper Verification of Cryptographic Signature
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Go toolchain | cmd/go |
Affected:
0 , < 1.25.13
(semver)
Affected: 1.26.0-0 , < 1.26.6 (semver) Affected: 1.27.0-0 , < 1.27.0-rc.3 (semver) |
guessed | |
| golang.org/x/mod | golang.org/x/mod/sumdb/tlog |
Affected:
0 , < 0.40.0
(semver)
|
guessed |
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}
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}
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