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CVE-2026-49422— Use-after-free in TCP RACK stack option handler

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.

RACK 的 setsockopt(2) 处理程序在从用户空间复制选项数据时释放了连接锁，随后重新获取该锁。在重新获取锁之后，它会验证 TCP 协议栈是否仍被当前连接使用，但未重新加载指向该连接的每连接控制块（per-connection control block）的指针。如果用户空间在此时间窗口内两次切换协议栈，则该检查会通过，但保存的指针将指向已释放的内存。 此漏洞可能被未经授权的本地用户利用，以实现权限提升。

AI Predicted 7.8 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-2026-49422

Vulnerability Information
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Vulnerability Title
Use-after-free in TCP RACK stack option handler
Source: CVE Program / CVE List V5
Vulnerability Description
The RACK setsockopt(2) handler drops the connection lock in order to copy option data from userspace, then reacquires the lock. After reacquiring, it verifies that the TCP stack had not been switched away, but did not reload its pointer to the stack's per-connection control block. If userspace switches stacks twice during this window, the check will succeed but the saved pointer will refer to freed memory. The bug may be exploitable by an unprivileged local user to escalate privileges.
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 ~ p1 -

II. Public POCs for CVE-2026-49422

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III. Intelligence Information for CVE-2026-49422

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Vendor Advisories for CVE-2026-49422 (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-2026-49421 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-2026-49422

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