CVE-2023-39320: Arbitrary code execution via go.mod toolchain directive in cmd/go

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-09-08 · updated 2026-06-17
Weakness: CWE-94

Description

The go.mod toolchain directive, introduced in Go 1.21, can be leveraged to execute scripts and binaries relative to the root of the module when the "go" command was executed within the module. This applies to modules downloaded using the "go" command from the module proxy, as well as modules downloaded directly using VCS software.

Affected products

Go: from 1.21.0 before 1.21.1 — fixed in 1.21.1

How to fix

Upgrade to a fixed version: Go 1.21.1. Check the vendor advisory for mitigations.

References

https://go.dev/cl/526158
https://go.dev/issue/62198
https://groups.google.com/g/golang-dev/c/2C5vbR-UNkI/m/L1hdrPhfBAAJ
https://pkg.go.dev/vuln/GO-2023-2042
https://security.gentoo.org/glsa/202311-09
https://security.netapp.com/advisory/ntap-20231020-0004/
https://go.dev/cl/526158
https://go.dev/issue/62198
https://groups.google.com/g/golang-dev/c/2C5vbR-UNkI/m/L1hdrPhfBAAJ
https://pkg.go.dev/vuln/GO-2023-2042
https://security.gentoo.org/glsa/202311-09
https://security.netapp.com/advisory/ntap-20231020-0004/

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