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CVE-2026-58083— Use-after-free in kqueue copy-on-fork

Quick assessment

Affected
FreeBSD FreeBSD
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在通过 fork 系统调用复制 knote（kevent 通知）期间，带有基于定时器的过滤器的 knote 可能在复制完成之前触发并被入队到 kqueue 的活动列表中。复制例程未考虑到这种情况，可能导致新的 knote 被重复入队，从而损坏活动列表。此外，复制例程在读取 knote 状态时未持有适当的锁，进一步引发了竞态条件。 未经特权的本地用户可以利用此漏洞在内核中触发 use-after-free 漏洞，可能导致权限提升。

AI Predicted 7.8 Difficulty: Moderate EPSS 0.12% · P2

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 1

VendorProduct Version RangeStatus
FreeBSD FreeBSD 15.1-RELEASE< p2 affected
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I. Basic Information for CVE-2026-58083

Vulnerability Information
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Vulnerability Title
Use-after-free in kqueue copy-on-fork
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
FreeBSD FreeBSD 15.1-RELEASE ~ p2 -

II. Public POCs for CVE-2026-58083

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III. Intelligence Information for CVE-2026-58083

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Vendor Advisories for CVE-2026-58083 (1)

Same Patch Batch · FreeBSD · 2026-08-19 · 23 CVEs total

CVE-2026-49426 Incorrect audit records for ptrace(2) syscall requests
CVE-2026-58087 Heap out-of-bounds access in semctl(2)
CVE-2026-58088 Race condition in ELF core dump segment counting
CVE-2026-58084 Kernel stack disclosure via timer_settime(2)
CVE-2026-58085 Missing MAC validation in wg(4) packet decryption
CVE-2026-58086 ktrace(2) privilege incorrectly validated in jails
CVE-2026-49425 Kernel stack disclosure in 32-bit compatibility support
CVE-2026-49424 Kernel stack disclosure in Linux compatibility layer
CVE-2026-58081 Heap based buffer overflow in iconv(3)
CVE-2026-58082 Stack based buffer overflow in iconv(3)
CVE-2026-49423 Remote DOS via uninitialized memory access in KTLS receive
CVE-2026-49418 Use-after-free in device pager page list
CVE-2026-49427 posixshm: largepage shared memory objects not explicitly wired
CVE-2026-49428 posixshm: system calls can incorrectly free memory of largepage objects
CVE-2026-49420 Buffer overflow in libalias RTSP handler
CVE-2026-49422 Use-after-free in TCP RACK stack option handler
CVE-2026-49421 unlinkat(2) ignores AT_RESOLVE_BENEATH flag
CVE-2026-49430 Kernel heap overflow in ZFS_IOC_RECV_NEW ioctl
CVE-2026-49429 Kernel heap overflow in ZFS_IOC_USERSPACE_MANY ioctl
CVE-2026-49431 Incorrect user validation in ZFS_IOC_SET_PROP ioctl

Showing top 20 of 23 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: FreeBSD
Same vendor: FreeBSD
Same weakness: CWE-416

V. Comments for CVE-2026-58083

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