CVE-2026-12634 (GCVE-0-2026-12634)
Vulnerability from cvelistv5 – Published: 2026-08-19 20:37 – Updated: 2026-08-20 15:26
VLAI
EPSS
VEX
Title
Out-of-bounds stack write in the settings NVS backend from over-reported nvs_read length
Summary
The NVS backend of the Zephyr settings subsystem (subsys/settings/src/settings_nvs.c) reads stored setting-name entries into fixed 74-byte stack buffers and NUL-terminates them with buf[rc] = '\0', where rc is the return value of nvs_read(). Per its contract, nvs_read() returns the full stored entry length (wlk_ate.len), which can exceed the supplied buffer length — only MIN(len, stored_len) bytes are actually copied, but the return value may be much larger, bounded only by the NVS sector size. Three sites (settings_nvs_cache_match(), settings_nvs_load(), and settings_nvs_save()) used this value directly as the NUL index without clamping, so an oversized stored name entry causes a single \0 byte to be written past the end of the stack buffer at an attacker-influenced offset (CWE-787).
The oversized entry cannot arise through the normal settings API, where names are bounded by SETTINGS_MAX_NAME_LEN. It requires an actor able to write the flash that backs the settings partition — a co-resident or untrusted component sharing the flash device, a malicious settings image/restore, or offline/physical flash access (a shared-flash threat model). The malformed entry is parsed when settings_load() runs at boot or subsystem init, or during settings_save().
The out-of-bounds write is a single NUL byte at an offset equal to the crafted entry length (up to the NVS sector size), so the practical impact is a crash or denial of service and limited stack corruption rather than reliable code execution. There is no confidentiality impact, and the path is not reachable from the network through the ordinary settings interface. The fix skips any entry whose nvs_read() length is greater than or equal to the buffer size before performing the NUL store.
Severity
5.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-20 15:15 UTC
CWE
- CWE-787 - bounds
Assigner
References
2 references
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| zephyrproject | zephyr |
Affected:
2.0.0 , < 4.5.0
(semver)
|
guessed |
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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