CVE-2026-105280 hexpm CVE debrief

Who should care

Defenders responsible for package management, especially those using hexpm hex, should assess exposure and verify the integrity of package tarballs fetched using mix hex.package fetch. This vulnerability may impact environments where package mirrors are configured.

Why it matters

CVE-2026-105280 is a medium-severity vulnerability in hexpm hex that allows a package mirror to substitute the tarball written to standard output by mix hex.package fetch. Defenders should prioritize verifying the integrity of package tarballs and review package mirrors to prevent potential substitution.

• Verify the integrity of package tarballs fetched using mix hex.package fetch to prevent potential substitution by a package mirror.
• Review and update package mirrors to ensure they do not serve altered bytes.
• Implement compensating controls to monitor and validate package tarballs.

Technical summary

The hexpm hex package has an Improper Validation of Integrity Check Value vulnerability, which allows a package mirror to substitute the tarball written to standard output by mix hex.package fetch. This occurs because the standard output branch of mix hex.package fetch writes the bytes returned by Hex.SCM.fetch/3 without comparing the fetched tarball's inner and outer checksums with the repository's signed registry.

Defensive priority

Defenders should prioritize verifying the integrity of package tarballs fetched using mix hex.package fetch, especially in environments where package mirrors may be configured.

Recommended defensive actions

• Verify the integrity of package tarballs fetched using mix hex.package fetch
• Review and update package mirrors to ensure they do not serve altered bytes
• Implement compensating controls to monitor and validate package tarballs
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and source item provide details on the Improper Validation of Integrity Check Value vulnerability in hexpm hex, which allows a package mirror to substitute the tarball written to standard output by mix hex.package fetch. However, the corpus does not provide information on actual exploitation or affected versions beyond those specified.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.