CVE-2025-9557: zephyrproject-rtos Zephyr · Classic Buffer Overflow
Affects zephyrproject-rtos ZephyrSource CVE Database V5
Not known to be exploited · CVSS 7.6 High : upgrade to 4.2.2 soon.
Data as of 25 Oct 2026, 19:02 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.2.2
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 26 Nov 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.
What to do
Upgrade zephyrproject-rtos Zephyr to 4.2.2.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| zephyrproject-rtosZephyr | Affected
| Fixed in
|
GitHubzephyrproject-rtos/zephyrpkg:github/zephyrproject-rtos/zephyrOther threats | Affected
| Fixed in– |
GitHubZephyrpkg:github/ZephyrOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Until patches are deployed, implement strict input validation and boundary checks at the application layer to prevent malformed data from triggering the overflow. Network segmentation is critical to isolate Zephyr-based devices from untrusted or less secure network segments, reducing the risk of exploitation via adjacent network vectors. Employ intrusion detection systems (IDS) and anomaly detection tools tailored to embedded device traffic to identify suspicious activity indicative of exploitation attempts. Regularly audit and update device firmware and software to minimize exposure. For critical systems, consider deploying runtime protections such as memory protection units (MPUs) or hardware-enforced isolation features to mitigate the impact of buffer overflows. Finally, maintain an inventory of all devices running Zephyr to ensure comprehensive coverage of mitigation efforts.
Description
An out-of-bound write can lead to an arbitrary code execution. Even on devices with some form of memory protection, this can still lead to a crash and a resultant denial of service.