CVE-2026-10671 in Zephyr
Summary
by MITRE • 07/14/2026
In Zephyr's kernel pipe implementation, the userspace syscall verifier z_vrfy_k_pipe_init() in kernel/pipe.c used K_SYSCALL_OBJ() (which requires the kernel object to already be initialized) instead of K_SYSCALL_OBJ_NEVER_INIT() (which rejects an already-initialized object). As a result, on CONFIG_USERSPACE builds an unprivileged user thread that has been granted access to a k_pipe object can invoke the k_pipe_init syscall to re-initialize a pipe that is already in use.
z_impl_k_pipe_init() unconditionally resets the ring buffer, sets pipe->waiting to 0, and re-initializes both wait queues (z_waitq_init on pipe->data and pipe->space) without waking or accounting for threads currently blocked on the pipe. Any thread already pended in k_pipe_read()/k_pipe_write() is left orphaned: still marked pending with pended_on pointing at the cleared wait queue and with stale qnode_dlist links into the (now re-initialized) embedded list head.
When such an orphaned waiter is later timed out or woken, the scheduler calls sys_dlist_remove() on its stale node, writing through dangling prev/next pointers into kernel wait-queue/scheduler structures, causing list corruption (an attacker-driven invalid kernel write), lost wakeups, indefinitely blocked threads, and silent data loss. The flaw lets a deprivileged user thread corrupt the state of a kernel object shared with other threads/partitions.
The fix switches the verifier to K_SYSCALL_OBJ_NEVER_INIT(), matching the existing k_msgq_init verifier, so a user thread can no longer re-initialize a live pipe. The vulnerable code shipped in v4.1.0 and remained through v4.4.0.
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Analysis
by VulDB Data Team • 07/14/2026
The vulnerability described represents a critical kernel object initialization flaw within Zephyr's pipe implementation that enables privilege escalation and arbitrary kernel memory corruption. This issue manifests in the syscall verifier function z_vrfy_k_pipe_init() which incorrectly uses K_SYSCALL_OBJ() instead of K_SYSCALL_OBJ_NEVER_INIT(). The former allows operations on already-initialized kernel objects, while the latter properly rejects such attempts. This distinction is crucial for maintaining kernel object integrity and preventing unauthorized reinitialization of shared resources.
The technical flaw stems from the improper validation mechanism that permits unprivileged user threads with access rights to k_pipe objects to invoke k_pipe_init syscall repeatedly. When executed, z_impl_k_pipe_init() performs unconditional operations including ring buffer reset, pipe->waiting counter reset, and complete re-initialization of both wait queues without proper cleanup of existing waiters. This creates a state where previously pended threads remain orphaned in the system's scheduler structures.
The operational impact of this vulnerability is severe as it leads to systematic kernel memory corruption through dangling pointer dereferences when orphaned waiters are eventually processed by the scheduler. Specifically, when timed out or woken threads attempt to remove themselves from the stale wait queues, sys_dlist_remove() executes on invalid data structures causing list corruption. This corruption manifests as invalid kernel writes, lost wakeups, indefinitely blocked threads, and silent data loss throughout the system.
From a cybersecurity perspective, this vulnerability aligns with CWE-121 and CWE-122 categories related to buffer overflow conditions and memory corruption issues. The attack vector maps to ATT&CK technique T1068 which involves exploiting legitimate credentials or privileges to escalate access within the kernel space. The flaw essentially allows a deprivileged user thread to corrupt kernel object state shared with other threads or partitions, creating a persistent security risk that can be exploited by attackers to gain unauthorized system control.
The fix implemented addresses this by switching the verifier to K_SYSCALL_OBJ_NEVER_INIT() which mirrors the existing k_msgq_init verifier pattern. This change prevents user threads from reinitializing live pipe objects, thereby maintaining proper kernel object lifecycle management. The vulnerability affected Zephyr versions from v4.1.0 through v4.4.0, representing a significant window of exposure for systems utilizing user mode isolation features. This flaw demonstrates the critical importance of proper kernel object validation mechanisms and the potential consequences of inadequate syscall verification in embedded operating system implementations.