# CVE-2026-15890: AEAD nonce reuse in Zephyr secure_storage ITS default nonce provider due to missing thread synchronization > Concurrent writes to the same secure storage entry can reuse AEAD nonces, allowing attackers with raw storage access to recover plaintext secrets or forge entries. - **Severity:** Medium 5.3 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** No - **Published:** 21 Sep 2026 - **Updated:** 15 Oct 2026 - **Also known as:** GHSA-23jw-7xv2-xr28 ## What is CVE-2026-15890? CVE-2026-15890 is a medium-severity vulnerability in zephyrproject zephyr, published on 21 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim. ### Official 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. Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization), CWE-323 (Reusing a Nonce, Key Pair in Encryption) ## Which versions are affected by CVE-2026-15890? ## How do I fix CVE-2026-15890? No fix has been published for CVE-2026-15890 yet. Limit exposure of the affected software until one is available. ## Is CVE-2026-15890 being exploited? There is no known exploitation of CVE-2026-15890 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-15890 and fix it if it is affected. What it is: CVE-2026-15890 is a medium-severity vulnerability in zephyrproject zephyr, published on 21 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-15890 in the wild and no public exploit code. Affected product: zephyrproject zephyr. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-15890/ (Markdown: https://insights.sbomify.com/CVE-2026-15890/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-15890 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15890 - OSV: https://osv.dev/vulnerability/CVE-2026-15890 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-15890/ Summaries are generated and may contain mistakes; the official description above is the record.