Quick answers
- Is CVE-2026-101003 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-101003 being exploited in the wild.
- How severe is CVE-2026-101003?
- Medium severity, with a CVSS score of 5.3, published 28 September 2026.
- Which products and versions are affected?
- Cesanta Mongoose up to 7.21.
- Is there a fix for CVE-2026-101003?
- A patch was published on 2026-06-23: Patch released in version 7.22 (commit a9df523f76f43a38bd53b4232b9cfd4c16869e71) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-101003 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-101003?
- Check whether you run Cesanta Mongoose at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A stack-based buffer overflow vulnerability exists in the MQTT broker component of Mongoose, specifically in the fn function within tutorials/mqtt/mqtt-server/main.c. The vulnerability can be exploited remotely without authentication by sending a crafted MQTT message. A patch was released in version 7.22, committed as a9df523f76f43a38bd53b4232b9cfd4c16869e71.
Affected products
- Cesanta Mongoose up to 7.21
Timeline
- 2026-09-28: disclosed: Vulnerability disclosed and CVSS assessed at 5.3
- 2026-06-23: patched: Patch released in version 7.22 (commit a9df523f76f43a38bd53b4232b9cfd4c16869e71)