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CVE-2025-9557VulnerabilityPublished Updated

CVE-2025-9557: zephyrproject-rtos Zephyr · Classic Buffer Overflow

Affects zephyrproject-rtos ZephyrSource CVE Database V5

0

Not known to be exploited · CVSS 7.6 High : upgrade to 4.2.2 soon.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score
7.6High
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 Nov 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
zephyrproject-rtosZephyrAffected
  • <4.2.2
Fixed in
  • 4.2.2
GitHubzephyrproject-rtos/zephyrpkg:github/zephyrproject-rtos/zephyrOther threatsAffected
  • *
Fixed in–
GitHubZephyrpkg:github/ZephyrOther threatsAffected
  • <4.2.2
Fixed in
  • 4.2.2

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.‬

References

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