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CVE-2026-56289 GNU CVE debrief

CVE-2026-56289 is a denial of service vulnerability in GNU patch. The vulnerability is caused by improper validation of hunk line offsets in unified-diff input. A specially crafted patch can specify an extremely large line number, causing the application to enter an effectively infinite processing loop while attempting to locate the requested position. This results in excessive CPU consumption and prevents the process from completing. An attacker can trigger this behavior by supplying a malicious patch file, causing the utility to become unresponsive and require manual termination. Users of GNU patch, especially those who process patches from untrusted sources, should be aware of this vulnerability and take steps to mitigate it.

Vendor
GNU
Product
patch
CVSS
MEDIUM 4.6
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-09
Original CVE updated
2026-07-13
Advisory published
2026-07-09
Advisory updated
2026-07-13

Who should care

Users of GNU patch, especially those who process patches from untrusted sources, should be aware of this vulnerability and take steps to mitigate it. This includes validating the source of patches and ensuring that they are properly formatted before processing them. Operators, platform administrators, vulnerability management teams, and security teams may be impacted.

Technical summary

The vulnerability is caused by improper validation of hunk line offsets in unified-diff input. When a specially crafted patch is supplied, the application enters an infinite processing loop, resulting in excessive CPU consumption and preventing the process from completing. This issue affects GNU patch deployments. Users should validate patch sources and format. The issue has been fixed in the commit faba04ef4f2b410257f76c1b9dc85e350929c4b9. Affected product deployments should be identified, and owners assigned for follow-up. Official advisories or CVE records should be reviewed to validate affected scope, severity, and vendor guidance. Vendor-supported updates or mitigations should be planned through normal change control where exposure is confirmed.

Defensive priority

Medium

Recommended defensive actions

  • Validate the source of patches and ensure they are properly formatted before processing them.
  • Implement input validation and sanitization to prevent malicious patches from being processed.
  • Monitor system resources and terminate unresponsive processes.
  • Apply the patch fix provided by the vendor.
  • 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

The CVE record was published on 2026-07-09T11:16:40.840Z and was last modified on 2026-07-13T14:10:56.943Z. The NVD entry is currently Analyzed. Evidence is limited to CVE and NVD information. Defenders should verify patch application and system responsiveness.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-56289 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-56289

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

  • CVE-2026-56289 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-56289

    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.