In short
- CVE-2026-56865 is a HIGH (CVSS 8.4) vulnerability affecting golang.org/x/mod, toolchain.
- Chance of exploitation in the next 30 days (EPSS): 0.13%, higher than 2.5% of all vulnerabilities.
- Fix: update to 0.40.0, 1.26.6, 1.27.0-rc.3, 1.25.13 or later.
| Package | Affected versions | Patched versions |
|---|
| golang.org/x/mod Go | < 0.40.0
| 0.40.0
|
| toolchain Go | ≥ 1.26.0-0, < 1.26.6≥ 1.27.0-0, < 1.27.0-rc.3< 1.25.13
| 1.26.61.27.0-rc.31.25.13
|
Description
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
NVD description
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
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