zephyrproject zephyr up to 4.4.x Dynamic Kernel Object Tracking userspace.c k_object_wordlist_foreach use after free

Summaryinfo

A vulnerability was found in zephyrproject zephyr up to 4.4.x. It has been classified as very critical. The impacted element is the function k_object_wordlist_foreach of the file kernel/userspace/userspace.c of the component Dynamic Kernel Object Tracking. The manipulation leads to use after free. This vulnerability is traded as CVE-2026-10667. An attack has to be approached locally. There is no exploit available.

Detailsinfo

A vulnerability was found in zephyrproject zephyr up to 4.4.x and classified as very critical. This issue affects the function k_object_wordlist_foreach of the file kernel/userspace/userspace.c of the component Dynamic Kernel Object Tracking. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Zephyr's dynamic kernel-object tracking (kernel/userspace/userspace.c, formerly kernel/userspace.c) maintains a doubly-linked list (obj_list) of dynamically allocated kernel objects. Iteration over this list in k_object_wordlist_foreach() was performed under lists_lock using the SAFE iterator (which caches the next node), but list removal and freeing of nodes was performed under different, disjoint spinlocks: objfree_lock in k_object_free() and obj_lock in unref_check(). On an SMP system, while one CPU iterated obj_list under lists_lock, another CPU could unlink and k_free() the dyn_obj node that the iterator had cached as its next pointer, causing the iterator to dereference freed kernel memory (use-after-free / dangling list traversal). All of the racing operations are reachable from unprivileged user-mode threads via system calls: k_object_alloc/k_object_alloc_size and k_object_release drive removals through unref_check() (under obj_lock), while k_thread_abort and thread creation drive the iteration through k_thread_perms_all_clear()/k_thread_perms_inherit() (under lists_lock). A deprivileged user thread on a CONFIG_SMP + CONFIG_USERSPACE build can therefore corrupt the kernel's object-tracking structures across the userspace security boundary, yielding kernel memory corruption (potential privilege escalation) or a kernel crash (denial of service). The fix removes objfree_lock and serializes every obj_list modification under lists_lock, including holding it across find+remove in k_object_free() and around unref_check() in k_thread_perms_clear(). Affects CONFIG_SMP+CONFIG_USERSPACE+CONFIG_DYNAMIC_OBJECTS configurations; the defect dates to the 2019 spinlockification (commit 8a3d57b6cc6, first released in v1.14.0) and shipped through v4.4.0.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-10667 since 06/02/2026. The exploitation is known to be easy. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/12/2026).

Upgrading to version 4.5.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-43244). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

• Project Management Software

Vendor

• zephyrproject

Name

• zephyr

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4

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CPE 2.2info

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Be aware that VulDB is the high quality source for vulnerability data.

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