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CVE-2026-12366— Use-after-free freeing an armed dynamically-allocated k_timer in Zephyr userspace object disposal

Quick assessment

Affected
zephyrproject zephyr
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.

Zephyr Project zephyr是Zephyr Project组织开源的一个面向物联网设备的实时操作系统。 Zephyr Project zephyr 1.12.0版本至4.5.0之前版本存在资源管理错误漏洞，该漏洞源于动态内核对象释放路径在清理对象时未处理K_OBJ_TIMER类型，导致释放后重用，可能允许攻击者造成内核堆内存破坏，实现沙箱逃逸和权限提升。

CVSS 8.8 · High EPSS 0.17% · P5

Affected Version Matrix 1

VendorProduct Version RangeStatus
zephyrproject zephyr 1.12.0< 4.5.0 affected
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I. Basic Information for CVE-2026-12366

Vulnerability Information
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Vulnerability Title
Use-after-free freeing an armed dynamically-allocated k_timer in Zephyr userspace object disposal
Source: CVE Program / CVE List V5
Vulnerability Description
Zephyr's dynamic kernel-object disposal path unref_check() in kernel/userspace/userspace.c frees an object's storage (k_free(dyn->data)) once its reference count reaches zero, after running a per-object-type cleanup. The cleanup switch handled only K_OBJ_MSGQ and K_OBJ_STACK; there was no K_OBJ_TIMER case. A dynamically-allocated, initialized, and armed k_timer keeps its embedded struct _timeout dnode linked in the global timeout queue (_timeout_q), so freeing the timer storage without cancelling the timeout leaves a dangling node in that queue. When the timer next expires, the timeout machinery walks _timeout_q and invokes z_timer_expiration_handler() on the freed node, dereferencing and writing freed (and reusable) kernel heap in kernel/ISR context. This is a deterministic use-after-free that does not depend on SMP: the queued node is simply never unlinked at free time. The disposal is reachable from an unprivileged user thread under CONFIG_USERSPACE + CONFIG_DYNAMIC_OBJECTS: a thread that holds the last permission on such a timer drops it via the k_object_release() syscall (or by exiting, through k_thread_perms_all_clear()), and can arm the timer itself via the k_timer_start() syscall. The free and the expiration handler run at kernel privilege while the actor is a user thread, so the bug is a sandbox-escape memory-corruption primitive usable for privilege escalation. The fix adds k_timer_cleanup() (cancel the timeout and wait for any in-flight handler) and calls it for K_OBJ_TIMER before freeing.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
释放后使用
Source: CVE Program / CVE List V5
Vulnerability Title
Zephyr Project zephyr 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Zephyr Project zephyr是Zephyr Project组织开源的一个面向物联网设备的实时操作系统。 Zephyr Project zephyr 1.12.0版本至4.5.0之前版本存在资源管理错误漏洞，该漏洞源于动态内核对象释放路径在清理对象时未处理K_OBJ_TIMER类型，导致释放后重用，可能允许攻击者造成内核堆内存破坏，实现沙箱逃逸和权限提升。
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
zephyrproject zephyr 1.12.0 ~ 4.5.0 -

II. Public POCs for CVE-2026-12366

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III. Intelligence Information for CVE-2026-12366

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Patches & Fixes for CVE-2026-12366 (1)

Vendor Advisories for CVE-2026-12366 (1)

Same Patch Batch · zephyrproject · 2026-08-14 · 4 CVEs total

CVE-2026-12364 8.4 HIGH Missing user-space pointer validation in logging syscall z_log_msg_static_create allows ke
CVE-2026-12365 5.8 MEDIUM Use-after-free in Zephyr delayable work-queue cancellation under SMP timing race
CVE-2026-12363 4.2 MEDIUM Out-of-bounds write in LoRaWAN fragmented transport from a fragment index of 0

IV. Related Vulnerabilities

Same product: zephyr
Same vendor: zephyrproject
Same weakness: CWE-416

V. Comments for CVE-2026-12366

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