CVE-2026-39817

Description

The "go tool pack" subcommand (usually used only by the compiler as an internal tool with known-good inputs) does not sanitize output filenames. Extracting a malicious archive file with the "pack" subcommand can write files to arbitrary locations on the filesystem.

CVSS Metrics

• v3.1•MEDIUM•Score: 5.9CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N

EPSS Trends

Current EPSS score: 0.01%• Percentile: 0%

Techniques & Countermeasures

• CWE-787•Out-of-bounds Write

  The product writes data past the end, or before the beginning, of the intended buffer.

Affected Systems

• go toolchain•cmd/go

  < 1.25.10 | ≥ 1.26.0-0, < 1.26.3

• golang•go

  < 1.25.10 | ≥ 1.26.0, < 1.26.3

• Go•toolchain

  ≥ 1.26.0-0, < 1.26.3

References (4)

• https://go.dev/issue/78778
• https://go.dev/cl/767520
• https://groups.google.com/g/golang-announce/c/qcCIEXso47M
• https://pkg.go.dev/vuln/GO-2026-4979