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VulnerabilityPublished Updated

CVE-2026-39817: Go toolchain cmd/go · Path Traversal

Affects Go toolchain cmd/goSource CVE Database V5

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Not known to be exploited · CVSS 5.9 Medium : upgrade to 1.26.3 or 1.25.10 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.26.3, 1.25.10
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 7 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade Go toolchain cmd/go to 1.26.3 or 1.25.10.

Affected software

ProductAffectedFixed in
Go toolchaincmd/goAffected
  • >=1.26.0-0 <1.26.3
Fixed in
  • 1.26.3
Go toolchaincmd/goAffected
  • <1.25.10
Fixed in
  • 1.25.10
Gocmd/gopkg:golang/cmd/goOther threatsAffected
  • <1.25.10
  • >=1.26.0-0 <1.26.3
Fixed in
  • 1.25.10
  • 1.26.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, users should exercise caution when extracting archives with the 'go tool pack' subcommand, especially from untrusted sources. Avoid processing untrusted archives to mitigate risk.

Description

CVE-2026-39817 is a medium-severity path traversal vulnerability in the Go toolchain's cmd/go component, specifically affecting the 'go tool pack' subcommand. This flaw allows a malicious archive to write files to arbitrary filesystem locations due to improper sanitization of output filenames when extracting archives. It affects Go versions up to 1.26.0-0.

References

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