CVE-2026-94447: Checksum database bypass for golang.org/toolchain in cmd/go

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-08 · updated 2026-10-15
Weakness: CWE-354

Description

Previously, a user operating inside of a malicious Go project that defines a bogus golang.org/toolchain go.sum entry and operates a malicious GOMODPROXY the user chooses to use can bypass the intended checksum. We now ensure that golang.org/toolchain always goes to the network for the canonical checksum.

Affected products

Go: before 1.26.9; from 1.27.0-0 before 1.27.2 — fixed in 1.26.9, 1.27.2

How to fix

Upgrade to a fixed version: Go 1.26.9, 1.27.2. Check the vendor advisory for mitigations.

References

https://go.dev/cl/840785
https://go.dev/issue/81834
https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
https://pkg.go.dev/vuln/GO-2026-6602

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