CVE-2026-56864: CWE-347: Improper Verification of Cryptographic Signature in Go toolchain cmd/go
A malicious GOSUMDB was capable of serving arbitrary module content not contained within the transparency log. This attack allows for a coordinating GOPROXY and GOSUMDB to serve a client malicious module content that cannot be detected by evaluating the transparency log. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy
AI Analysis
Technical Summary
This vulnerability (CWE-347) in the Go toolchain's cmd/go allows a malicious GOSUMDB to serve arbitrary module content that bypasses the transparency log verification. This enables an attacker controlling both GOPROXY and GOSUMDB to deliver malicious modules to clients without detection by the transparency log. The affected versions include =1.26.0-0, =1.27.0-0, <1.25.13, >=1.26.0-0 <1.26.6, and <0.40.0. There is no CVSS score or official remediation level published yet.
Potential Impact
Clients using affected versions of the Go toolchain may receive malicious module content that is not recorded in the transparency log, potentially leading to supply chain compromise. The attack requires control of both GOPROXY and GOSUMDB to coordinate delivery of malicious modules undetectable by normal verification mechanisms.
Mitigation Recommendations
No official patch or remediation is currently documented. Users are advised to check if they have been affected by removing go.sum, go.work.sum, and vendor/ directories and then running 'go mod tidy' to refresh module dependencies. Monitor vendor advisories for updates and patches.
CVE-2026-56864: CWE-347: Improper Verification of Cryptographic Signature in Go toolchain cmd/go
Description
A malicious GOSUMDB was capable of serving arbitrary module content not contained within the transparency log. This attack allows for a coordinating GOPROXY and GOSUMDB to serve a client malicious module content that cannot be detected by evaluating the transparency log. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy
CVSS v3.1
Score 7.5high
Affected software
Go toolchain
cmd/go
golang.org/x/mod
golang.org/x/mod/sumdb
pkg:golang/cmd/gopkg:golang/golang.org/x/mod/sumdbRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CWE-347) in the Go toolchain's cmd/go allows a malicious GOSUMDB to serve arbitrary module content that bypasses the transparency log verification. This enables an attacker controlling both GOPROXY and GOSUMDB to deliver malicious modules to clients without detection by the transparency log. The affected versions include =1.26.0-0, =1.27.0-0, <1.25.13, >=1.26.0-0 <1.26.6, and <0.40.0. There is no CVSS score or official remediation level published yet.
Potential Impact
Clients using affected versions of the Go toolchain may receive malicious module content that is not recorded in the transparency log, potentially leading to supply chain compromise. The attack requires control of both GOPROXY and GOSUMDB to coordinate delivery of malicious modules undetectable by normal verification mechanisms.
Mitigation Recommendations
No official patch or remediation is currently documented. Users are advised to check if they have been affected by removing go.sum, go.work.sum, and vendor/ directories and then running 'go mod tidy' to refresh module dependencies. Monitor vendor advisories for updates and patches.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Go
- Date Reserved
- 2026-06-23T15:10:49.354Z
- State
- PUBLISHED
Threat ID: 6a7e412ebf8831d539e05137
Added to database: 08/13/2026, 22:11:58 UTC
Last enriched: 08/13/2026, 22:27:27 UTC
Last updated: 09/29/2026, 01:47:43 UTC
Views: 84
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