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CVE-2026-56865

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

Description (CNA)

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

Affected (CNA)

Vendor / productVersions
Go toolchain / cmd/goaffected 0 before 1.25.13; affected 1.26.0-0 before 1.26.6; affected 1.27.0-0 before 1.27.0-rc.3
golang.org/x/mod / golang.org/x/mod/sumdb/tlogaffected 0 before 0.40.0

CWE

No CWE identifiers supplied.

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.