Use After Free in FreeBSD
CVE-2026-58083
While the kernel was copying knotes during fork, a knote with a timer-based filter could fire and be enqueued on the kqueue's active list before the copy was complete. The copy routine did not account for this and could enqueue the new knote a second time, corrupting the active list. In addition, the copy routine did not hold the appropriate locks while reading knote state, allowing further races. An unprivileged local user can trigger a use-after-free in the kernel, potentially leading to privilege escalation.
Vulnerability class: Use-After-Free
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.4 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.002 (5.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 5.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.001 · newest: 0.002 · change: +0.000
Affected products
- FreeBSD — versions 15.1
Weakness classification (CWE)
References
- security.freebsd.org/advisories/FreeBSD-SA-26:50.kqueue.asc (vendor-advisory, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-58083?
- CVE-2026-58083 is a high-severity vulnerability in FreeBSD, classified under Use After Free. CVSS score: 8.4/10. Published 2026-08-19.
- How severe is CVE-2026-58083?
- High severity. CVSS v3 base score is 8.4 out of 10.