Invoking "go bug" follows symlinks in predictable temporary filenames in cmd/go

MEDIUM 5.3CVE-2026-39819 · BIT-golang-2026-39819 · GO-2026-4978 · Published 07/05/2026 · updated 17/06/2026

In short

CVE-2026-39819 is a MEDIUM (CVSS 5.3) vulnerability affecting toolchain, go (golang).
Chance of exploitation in the next 30 days (EPSS): 0.18%, higher than 7.5% of all vulnerabilities.
Fix: update to 1.26.3, 1.25.10 or later.

Package	Affected versions	Patched versions
toolchain Go	`≥ 1.26.0-0, < 1.26.3< 1.25.10`	`1.26.31.25.10`
go golang	`≥ 1.26.0, < 1.26.3< 1.25.10`	`1.26.31.25.10`

Description

The "go bug" command writes to two files with predictable names in the system temporary directory (for example, "/tmp").

An attacker with access to the temporary directory can create a symlink in one of these names, causing "go bug" to overwrite the target of the symlink.

NVD description

The "go bug" command writes to two files with predictable names in the system temporary directory (for example, "/tmp"). An attacker with access to the temporary directory can create a symlink in one of these names, causing "go bug" to overwrite the target of the symlink.

References

go.dev/issue/78584 · REPORT
go.dev/cl/763882 · FIX
groups.google.com/g/golang-announce/c/qcCIEXso47M · WEB
pkg.go.dev/vuln/GO-2026-4978 · Vendor Advisory

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Package

Affected versions

Patched versions

toolchain

≥ 1.26.0-0, < 1.26.3< 1.25.10

1.26.31.25.10

golang

≥ 1.26.0, < 1.26.3< 1.25.10