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CVE-2026-66485 GNU CVE debrief

GNU cpio is vulnerable to uncontrolled memory allocation in the make_path function at src/makepath.c, allowing a denial of service via crafted archive. The function uses alloca to allocate stack memory based on argpath length, derived from an archive-controlled pathname during extraction. A malicious cpio archive with a sufficiently long nested pathname causes unbounded stack allocation, resulting in a stack overflow and crash of the cpio process. Users and administrators should review their inventory, ensure patching, and monitor for potential exploitation attempts. This issue has been fixed in commit 3cd514031371d8aeeaf2048aa10103e02831aaa9. Evidence from official CVE record and NVD detail supports this assessment.

Vendor
GNU
Product
cpio
CVSS
MEDIUM 4.6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-08-10
Original CVE updated
2026-08-28
Advisory published
2026-08-10
Advisory updated
2026-08-28

Who should care

Users and administrators of GNU cpio, especially those who extract archives from untrusted sources, should be aware of this vulnerability and take steps to mitigate it. This includes reviewing their inventory of GNU cpio installations, ensuring they are patched, and monitoring for potential exploitation attempts.

Technical summary

GNU cpio is vulnerable to an uncontrolled memory allocation in the make_path function at src/makepath.c. The function uses alloca to allocate stack memory based on the length of argpath, which is derived from an archive-controlled pathname during extraction. A malicious cpio archive containing a sufficiently long nested pathname causes an unbounded stack allocation, resulting in a stack overflow and crash of the cpio process. This issue can lead to a denial of service.

Defensive priority

GNU cpio vulnerability allows denial of service via crafted archive; prioritize patching and inventory checks.

Recommended defensive actions

  • Apply patch from commit 3cd514031371d8aeeaf2048aa10103e02831aaa9
  • Inventory and verify GNU cpio installations
  • Monitor for crafted cpio archives
  • Restrict archive extraction to trusted sources
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

CVE-2026-66485: GNU cpio vulnerable to uncontrolled memory allocation; fix in commit 3cd514031371d8aeeaf2048aa10103e02831aaa9; evidence from official CVE record and NVD detail. The vulnerability allows for a denial of service via crafted archive. Users should verify their GNU cpio installations and ensure they are not exposed to untrusted archive sources.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-66485 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-66485

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-66485 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-66485

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental 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.