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CVE-2026-49419— Jail reference count underflow

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.

FreeBSD是FreeBSD基金会开源的一款类Unix操作系统。 FreeBSD 15.1-RELEASE版本和15.0-RELEASE版本存在资源管理错误漏洞，该漏洞源于kern_jail_set()和kern_jail_get()函数在查找监狱描述符前释放调用者当前监狱的引用，错误处理路径可能重复释放引用，导致引用计数下溢，可能使正在使用的监狱结构被释放，从而导致拒绝服务或权限提升。

AI Predicted 8.5 Difficulty: Easy EPSS 0.47% · P38

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 2

VendorProduct Version RangeStatus
FreeBSD FreeBSD 15.1-RELEASE< p1 affected
15.0-RELEASE< p11 affected
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I. Basic Information for CVE-2026-49419

Vulnerability Information
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Vulnerability Title
Jail reference count underflow
Source: CVE Program / CVE List V5
Vulnerability Description
When the JAIL_AT_DESC flag is specified, kern_jail_set() and kern_jail_get() released the reference to the caller's current prison before looking up the jail descriptor. If the descriptor lookup failed, error-handling paths released the same reference a second time. An unprivileged local user can trigger a prison reference count underflow, which may cause the prison structure to be freed while still in use. When this is done on the jail host, the bug will generally result in an immediate panic. However, if the user is running in a jail, then it may be possible to exploit the bug to elevate privileges.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
引用计数的更新不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
FreeBSD 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FreeBSD是FreeBSD基金会开源的一款类Unix操作系统。 FreeBSD 15.1-RELEASE版本和15.0-RELEASE版本存在资源管理错误漏洞，该漏洞源于kern_jail_set()和kern_jail_get()函数在查找监狱描述符前释放调用者当前监狱的引用，错误处理路径可能重复释放引用，导致引用计数下溢，可能使正在使用的监狱结构被释放，从而导致拒绝服务或权限提升。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

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

II. Public POCs for CVE-2026-49419

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III. Intelligence Information for CVE-2026-49419

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Vendor Advisories for CVE-2026-49419 (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-2026-49421 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

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

IV. Related Vulnerabilities

Same product: FreeBSD
Same vendor: FreeBSD
Same weakness: CWE-911

V. Comments for CVE-2026-49419

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