ZephyrProject Zephyr up to 4.4.2 Kernel Object Management userspace.c dynamic_object_create size integer overflow

Summaryinfo

A vulnerability identified as very critical has been detected in ZephyrProject Zephyr up to 4.4.2. Impacted is the function dynamic_object_create of the file kernel/userspace/userspace.c of the component Kernel Object Management. The manipulation of the argument size leads to integer overflow. This vulnerability is traded as CVE-2026-19569. An attack has to be approached locally. There is no exploit available. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability, which was classified as very critical, has been found in ZephyrProject Zephyr up to 4.4.2. This issue affects the function dynamic_object_create of the file kernel/userspace/userspace.c of the component Kernel Object Management. The manipulation of the argument size with an unknown input leads to a integer overflow vulnerability. Using CWE to declare the problem leads to CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

dynamic_object_create() in kernel/userspace/userspace.c computed the backing allocation for a dynamically allocated kernel object as obj_size_get(otype) + size, and for thread stack elements as STACK_ELEMENT_DATA_SIZE(size) (a round-up plus fixed overhead), without checking either expression for unsigned wrap-around. A size close to SIZE_MAX makes the computed total wrap to a very small value, so the heap chunk handed out is a few bytes while the object descriptor is still tagged with the full requested type and registered in the kernel object table. The size argument reaches that arithmetic directly from user mode. k_object_alloc_size() is declared __syscall in include/zephyr/sys/kobject.h, its verifier z_vrfy_k_object_alloc_size() in kernel/userspace/userspace_handler.c is a bare pass-through, and z_object_alloc() only range-checks otype — nothing bounds size. The stack-element branch is additionally reachable through the k_thread_stack_alloc() syscall via kernel/dynamic.c. Because subsequent kernel-object validation checks only the object's type and initialization state, the undersized handle passes K_SYSCALL_OBJ_INIT()/K_SYSCALL_OBJ_NEVER_INIT(), and the matching init syscall (for example k_mutex_init(), k_sem_init(), or k_thread_create()) then writes a complete object over the truncated allocation. An unprivileged user-mode thread can therefore trigger a supervisor-mode out-of-bounds write into the kernel resource-pool heap, of a size and content it substantially controls, corrupting sys_heap chunk metadata and adjacent kernel objects. Under CONFIG_GEN_PRIV_STACKS the thread-stack branch additionally stores an attacker-influenced wild pointer as a user thread's privileged stack base. The practical result is escape from the CONFIG_USERSPACE sandbox — kernel-level code execution or at minimum kernel memory corruption and system compromise. Exploitation requires CONFIG_USERSPACE together with CONFIG_DYNAMIC_OBJECTS (also selected by CONFIG_DYNAMIC_THREAD under userspace), and a calling thread with an assigned resource pool. The fix rejects both overflowing computations and frees the partially built descriptor.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-19569 since 08/11/2026. 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 10/09/2026).

Applying the patch 85c1c4c21945d9b8fcef03216f1ccb2b27794e3d is able to eliminate this problem.

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Productinfo

Type

• Project Management Software

Vendor

• ZephyrProject

Name

• Zephyr

Version

• 4.4.0
• 4.4.1
• 4.4.2

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CPE 2.2info

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