# CVE-2026-12233: Uninitialized mutex in TLS trusted-credential backend causes kernel NULL-deref DoS under contention

Status: published. Published: 2026-08-12. Updated: 2026-11-04.

The PSA Protected Storage credential backend (subsys/net/lib/tls_credentials/tls_credentials_trusted.c) declared its credential-store mutex as a plain zero-filled static struct k_mutex credential_lock; and never called k_mutex_init() on it. A statically zero-filled k_mutex has an uninitialized wait queue (its dlist head/tail are NULL instead of the self-referential sentinels that k_mutex_init/K_MUTEX_DEFINE install). The uncontended lock path does not touch the wait queue, so the defect is latent and serialized use behaves correctly.

When two execution contexts contend on the lock, k_mutex_lock() pends the blocking thread on the wait queue via z_pend_curr(), which calls sys_dlist_append() on the zeroed list and dereferences a NULL tail pointer (tail->next = node), faulting the kernel. The lock is held during TLS handshake credential loading and by all credential add/get/delete operations, so a deployment performing concurrent TLS handshakes (for example a server handling multiple simultaneous connections from a remote peer) or a credential-management operation concurrent with a handshake can trigger the dereference.

The impact is a denial of service: a deterministic kernel panic / device reset on the first contention. There is no memory corruption beyond the NULL dereference and no confidentiality or integrity impact; mutual exclusion on the fast path remains correct. Exposure is limited to builds with CONFIG_TLS_CREDENTIALS_BACKEND_PROTECTED_STORAGE enabled (PSA Protected Storage / TF-M platforms); the default volatile RAM backend initializes its lock correctly and is unaffected.

The fix initializes the mutex statically with K_MUTEX_DEFINE(credential_lock), providing a valid wait queue so the contended path no longer touches a NULL list.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: zephyr) — https://github.com/zephyrproject-rtos/zephyr/commit/29581d586f3d68ec8bb1448b522e5470d4a06aa9

## Affected products and versions

- zephyrproject / zephyr (zephyr): ≥ 3.2.0; < 4.3.2 (affected, semver); ≥ 4.4.0; < 4.4.2 (affected, semver). Source: CNA: zephyr

## Severity and prioritization

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: CNA: zephyr

- CVSS 3.1: 5.9 (medium); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H; source: NVD: vulnerabilities@zephyrproject.org

- CISA KEV: No listing in collected sources

- EPSS: 0.51% as of 2026-11-03; percentile 43.27%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-665

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/zephyrproject-rtos/zephyr/commit/29581d586f3d68ec8bb1448b522e5470d4a06aa9 (CNA: zephyr; patch)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-57c4-xcq2-fqj7 (CNA: zephyr)

- https://github.com/zephyrproject-rtos/zephyr/commit/29581d586f3d68ec8bb1448b522e5470d4a06aa9 (vulnerabilities@zephyrproject.org)

- https://github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-57c4-xcq2-fqj7 (vulnerabilities@zephyrproject.org)

## Provenance

- CNA: zephyr: https://www.cve.org/CVERecord?id=CVE-2026-12233; retrieved 2026-11-04; source updated 2026-11-04

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12233; retrieved 2026-11-04; source updated 2026-11-04

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-12233; retrieved 2026-11-04; source updated Not reported

Revision: 82f0421b5514800fc9d3a6d0359f3272aa583cd44d5e1dd22dc47c891da7ff03

Canonical: https://y2.dev/cve/CVE-2026-12233

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