TI-2026-41833 Aliases CVE-2026-58083 GHSA-j94h-9p69-vhvm

Use-after-free in kqueue copy-on-fork

LOW 38CWE-416Published 2026-08-19 · Updated 2026-08-20

Key facts

Attack vector: Local
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-416 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00168 6th percentileScored 2026-11-07

Fix Fixed FreeBSD (FreeBSD): p2

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
FreeBSD	FreeBSD	15.1-RELEASE to before p2	p2	Patch available	CNA

FreeBSD VendorFreeBSD Affected 15.1-RELEASE to before p2 Fixed in p2 Patch available CNA

CPE configurations NVD · 4

CPE	Versions	Role	Vendor
cpe:2.3:o:freebsd:freebsd:15.1:-::::::	15.1	Vulnerable	FreeBSD
cpe:2.3:o:freebsd:freebsd:15.1:p1::::::	15.1 p1	Vulnerable	FreeBSD
cpe:2.3:o:freebsd:freebsd:15.1:rc2::::::	15.1 rc2	Vulnerable	FreeBSD
cpe:2.3:o:freebsd:freebsd:15.1:rc3-p1::::::	15.1 rc3-p1	Vulnerable	FreeBSD

cpe:2.3:o:freebsd:freebsd:15.1:-:*:*:*:*:*:* Versions 15.1 Vulnerable ·FreeBSD
cpe:2.3:o:freebsd:freebsd:15.1:p1:*:*:*:*:*:* Versions 15.1 p1 Vulnerable ·FreeBSD
cpe:2.3:o:freebsd:freebsd:15.1:rc2:*:*:*:*:*:* Versions 15.1 rc2 Vulnerable ·FreeBSD
cpe:2.3:o:freebsd:freebsd:15.1:rc3-p1:*:*:*:*:*:* Versions 15.1 rc3-p1 Vulnerable ·FreeBSD

Remediation

Fix · CNA FreeBSD (FreeBSD) Fixed in p2

Timeline

2026-10-02 Threatist record created from CVE-2026-58083
2026-10-03 Alias added: GHSA-j94h-9p69-vhvm

References

Advisory 1

https://security.freebsd.org/advisories/FreeBSD-SA-26:50.kqueue.asc

TI-2011-04182 Buffer overflow in libtelnet/encrypt.c in telnetd in FreeBSD 7.3 through 9.0, MIT… CVSS 2.0HIGH 10.0
TI-2007-03684 Integer overflow in print-bgp.c in the BGP dissector in tcpdump 3.9.6 and earlier allows… CVSS 3.1CRITICAL 9.8
TI-2002-00376 Integer overflow in xdr_array function in RPC servers for operating systems that use… CVSS 3.1CRITICAL 9.8
TI-2024-05929 Openssh: regresshion - race condition in ssh allows rce/dos CVSS 3.1HIGH 8.1
TI-2003-00437 Off-by-one error in the fb_realpath() function, as derived from the realpath function in… CVSS 3.1CRITICAL 9.8
TI-2003-00642 The prescan function in Sendmail 8.12.9 allows remote attackers to execute arbitrary code… CVSS 2.0HIGH 10.0

See all 576 →

Sources

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