CVE-2026-10681 — Security Box Score

CVE · referencelatest edition

Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-10681HIGH

zephyrproject zephyr — SMP race in `thread_idx_alloc()` lets concurrent `k_object_alloc(K_OBJ_THREAD)` callers share a kernel-object permission slot

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   L   H   L   N  U  H  H  H    7.0   .0008    0.4     —

AFFECTED
  Product  Versions  Fixed
  zephyr   2.0.0 –   —

TIMELINE
  Jun 2   Reserved by zephyr
  Jul 25  EXPLOIT PUBLISHED — CVE-2026-10681 (zephyrproject zephyr). Public exploit reference added.
  Jul 25  Published (CNA: zephyr)
  Aug 12  EXPLOIT PUBLISHED — CVE-2026-10681 (zephyrproject zephyr). Public exploit reference added.

CWE-362 · CNA: zephyr · CVSS v3.1 · 2 references · NVD status: Analyzed

Description

In Zephyr's userspace dynamic-objects subsystem, thread_idx_alloc() in kernel/userspace/userspace.c allocated a new thread permission index from the global _thread_idx_map[] bitmap without holding lists_lock. On SMP systems, two user-mode threads invoking the k_object_alloc(K_OBJ_THREAD) syscall concurrently can both observe the same low free bit, perform the same non-atomic RMW to clear it, and return the identical tidx. The two newly created K_OBJ_THREAD objects are then assigned the same thread_id, so the two user threads alias a single bit position in every kernel object's perms[] bitfield: any subsequent grant of access on a kernel object to one thread is implicitly a grant to the other, defeating userspace ACL isolation. A secondary lost-update window between the unlocked &=~BIT() in alloc and the locked |= BIT() in thread_idx_free() can also leak entries from the thread-index pool. The defect is reachable from any user-mode thread via the unrestricted __syscall k_object_alloc and is gated on CONFIG_USERSPACE, CONFIG_DYNAMIC_OBJECTS, and CONFIG_SMP. The flaw was introduced when the per-thread permission index was added in 2018 and is present in every release up to and including v4.4.0. Fixed by holding lists_lock across the bitmap RMW and the permissions clear (and inlining the obj_list traversal that previously took the lock itself).

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
June 2, 2026	Reserved	Reserved by zephyr
July 25, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-10681 (zephyrproject zephyr). Public exploit reference added.
July 25, 2026	Published	Published (CNA: zephyr)
August 12, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-10681 (zephyrproject zephyr). Public exploit reference added.

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
zephyrproject	zephyr	—	2.0.0	—

Weaknesses

CWE-362

References (2)

https://github.com/zephyrproject-rtos/zephyr/commit/862ea2fbbeb2ccdf8ff994b03e2e3b4405f2c37d [Patch]
https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-j693-5rh5-8g8h [Exploit, Patch, Vendor Advisory]

Authoritative record: CVE-2026-10681 at cve.org

Vendors: zephyrproject

Weaknesses: CWE-362

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-10681 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.