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CVE-2026-49421— unlinkat(2) ignores AT_RESOLVE_BENEATH flag

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.

实现 unlinkat(2) 和 funlinkat(2) 内核函数时，虽然对 AT_RESOLVE_BENEATH 标志进行了验证，但未将其传递至底层路径查找流程。该标志被静默丢弃，导致路径解析实际上并未受到限制。 若进程在使用 unlinkat(2) 或 funlinkat(2) 时配合 AT_RESOLVE_BENEATH 标志以约束路径解析范围，则实际上仍可能解析到起始目录之上的路径。依赖此标志进行路径 containment（限制）的调用者可能会意外删除目标目录树之外的文件。

AI Predicted 6.8 Difficulty: Moderate EPSS 0.13% · P3

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 4

VendorProduct Version RangeStatus
FreeBSD FreeBSD 15.1-RELEASE< p1 affected
15.0-RELEASE< p11 affected
14.4-RELEASE< p7 affected
14.3-RELEASE< p16 affected
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I. Basic Information for CVE-2026-49421

Vulnerability Information
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Vulnerability Title
unlinkat(2) ignores AT_RESOLVE_BENEATH flag
Source: CVE Program / CVE List V5
Vulnerability Description
The kernel function that implements unlinkat(2) and funlinkat(2) validated the AT_RESOLVE_BENEATH flag but failed to pass it through to the underlying path lookup. The flag was silently dropped, so path resolution was not actually restricted. A process that uses AT_RESOLVE_BENEATH with unlinkat(2) or funlinkat(2) to confine path resolution can in fact resolve paths above the starting directory. A caller relying on this flag for path containment may delete files outside the intended directory tree.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
对于放弃特权的检查不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
FreeBSD FreeBSD 15.1-RELEASE ~ p1 -

II. Public POCs for CVE-2026-49421

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III. Intelligence Information for CVE-2026-49421

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Vendor Advisories for CVE-2026-49421 (1)

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

CVE-2026-49423 Remote DOS via uninitialized memory access in KTLS receive
CVE-2026-58087 Heap out-of-bounds access in semctl(2)
CVE-2026-58088 Race condition in ELF core dump segment counting
CVE-2026-58083 Use-after-free in kqueue copy-on-fork
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-2026-49418 Use-after-free in device pager page list
CVE-2026-49426 Incorrect audit records for ptrace(2) syscall requests
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-2026-49430 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-273

V. Comments for CVE-2026-49421

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