Memory safety bugs in kqueue copy-on-fork implementation

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• vendor FreeBSD FreeBSDversion unspecified

How to fix CVE-2026-58099

• Recommended remediation

  A patch or advisory reference is linked. Open the original publisher for availability by product version.

• Official advisories

  • CIRCL Vulnerability Lookup · vulnerability.circl.lu
  • CVE.org · cve.org
  • FIRST EPSS · first.org
  • FreeBSD Security · freebsd.org
  • NIST NVD · nvd.nist.gov

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

1. Oct 15, 2026 · NIST NVD

   Detected

   When copying knotes from a parent kqueue to a child, the copy code did not correctly exclude marker knotes (used internally to track list traversal position) before marking them as in-flux and releasing the kqueue lock. If another thread freed a marker while the lock was dropped, the subsequent in-flux decrement operated on freed memory. An unprivileged local user may be able to exploit these race

2. Oct 15, 2026 · NIST NVD

   Updated

   When copying knotes from a parent kqueue to a child, the copy code did not correctly exclude marker knotes (used internally to track list traversal position) before marking them as in-flux and releasing the kqueue lock. If another thread freed a marker while the lock was dropped, the subsequent in-flux decrement operated on freed memory. An unprivileged local user may be able to exploit these race

3. Oct 16, 2026 · NIST NVD

   Updated

   When copying knotes from a parent kqueue to a child, the copy code did not correctly exclude marker knotes (used internally to track list traversal position) before marking them as in-flux and releasing the kqueue lock. If another thread freed a marker while the lock was dropped, the subsequent in-flux decrement operated on freed memory. An unprivileged local user may be able to exploit these race

Sources

• CIRCL Vulnerability LookupVulnerability recordCVE-2026-58099

  When copying knotes from a parent kqueue to a child, the copy code did not correctly exclude marker knotes (used internally to track list traversal position) before marking them as in-flux and releasing the kqueue lock. If another thread freed a marker while the lock was dropped,

  vulnerability.circl.lu
• CVE.orgVulnerability recordCVE-2026-58099

  Official CVE identifier

  cve.org
• FIRST EPSSExploitation probabilityCVE-2026-58099

  30-day exploitation probability 0.1%

  first.org
• FreeBSD SecurityVendor advisoryCVE-2026-58099

  CVE-2026-58099 is named by FreeBSD Security.

  freebsd.org
• NIST NVDVulnerability recordCVE-2026-58099

  When copying knotes from a parent kqueue to a child, the copy code did not correctly exclude marker knotes (used internally to track list traversal position) before marking them as in-flux and releasing the kqueue lock. If another thread freed a marker while the lock was dropped

  nvd.nist.gov

References

• Reference · security.freebsd.org

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.