CVE-2026-58099: freebsd Race Condition

Vulnerability summary

CVE-2026-58099 is a high (CVSS 7.0) Race Condition vulnerability in freebsd. EPSS estimates a 0.10% chance of exploitation in the next 30 days, higher than 0.6% of scored vulnerabilities.

Timeline

1. 15-10-2026
   PublishedVulnerability first disclosed.
2. 19-10-2026
   Last modifiedVulnerability information updated.

Description

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 races to escalate privileges.

• CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
• CWE-416Use After FreeThe product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.