AEAD nonce reuse in Zephyr secure_storage ITS default nonce provider due to missing thread synchronization

Summary

CVE	CVE-2026-15890
State	PUBLISHED
Assigner	zephyr
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-09-21 22:16:56 UTC
Updated	2026-09-22 19:41:24 UTC
Description	The default AEAD nonce provider for the PSA Internal Trusted Storage transform module, secure_storage_its_transform_aead_get_nonce() in subsys/secure_storage/src/its/transform/aead_get.c, stores its nonce counter in unsynchronized function-local static variables (s_nonce and s_nonce_initialized). Every ITS write obtains its AES-GCM or ChaCha20-Poly1305 nonce here via secure_storage_its_transform_to_store(). Because the function held no lock, two threads calling it concurrently race on the shared statics: the initialization path (psa_generate_random() followed by memcpy()) and the non-atomic increment-then-copy path can each hand the same nonce value to two distinct encryption operations, and can lose increments so the counter repeats values it was designed never to repeat. The ITS layer (secure_storage_its_set() in subsys/secure_storage/src/its/implementation.c) performs no serialization of its own, so concurrent same-UID writes reach the racy provider directly. Reusing a nonce with the same key under AES-GCM or ChaCha20-Poly1305 is a catastrophic AEAD failure: it leaks the XOR of the two plaintexts (ITS routinely stores secrets, including PSA persistent keys) and, for GCM, exposes the authentication key, enabling forgery of stored entries. Because the AEAD key is derived per entry UID, the security-relevant collision is two concurrent writes to the same UID both receiving the same nonce; an adversary able to read the raw backing storage can then exploit the reuse. Both ITS store back-ends shipped with Zephyr, zms.c and the settings/NVS back-end in settings.c, are log-structured flash stores with deferred garbage collection, so an entry superseded by a rewrite remains physically present in the partition until its sector is reclaimed. Two same-UID writes that race therefore leave both ciphertexts readable in the raw image at once, which is the condition the nonce reuse needs to be exploitable. The trigger remains narrow: both built-in key providers (DEVICE_ID_HASH and ENTRY_UID_HASH) salt the derived key with the entry UID, so reuse across different UIDs is harmless, and the exposure requires an application that writes the same UID concurrently from two threads. The fix serializes the provider with a K_MUTEX_DEFINE(s_nonce_mutex) held for the duration of nonce generation.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N

EPSS: 0.000620000 probability, percentile 0.000150000 (date 2026-09-23)

Problem Types: CWE-323 | CWE-362 | CWE-323 crypto | CWE-362 crypto

Version	Source	Type	Score	Severity	Vector
3.1	[email protected]	Secondary	5.3	MEDIUM	`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N`
3.1	CNA	CVSS	5.3	MEDIUM	`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N`

CVSS v3.1 Breakdown

Attack Vector

Local

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

Low

Availability

None

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Zephyrproject	Zephyr	affected 4.0.0 4.3.2 semver	Not specified
CNA	Zephyrproject	Zephyr	affected 4.4.0 4.4.2 semver	Not specified

References

Reference	Source	Link	Tags
github.com/zephyrproject-rtos/zephyr/security/advisories/GHSA-23jw-7xv2-...	[email protected]	github.com
github.com/zephyrproject-rtos/zephyr/commit/dc66397309248271df1fd0131d68...	[email protected]	github.com
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

There are currently no legacy QID mappings associated with this CVE.