Vulnerability in Cesanta Mongoose
CVE-2026-6985
A weakness has been identified in Cesanta Mongoose up to 7.20. This vulnerability affects the function handle_opt of the file /src/net_builtin.c of the component TCP Option Handler. This manipulation of the argument optlen causes infinite loop. The attack is possible to be carried out remotely. The exploit has been made available to the public and could be used for attacks. Upgrading to version 7.21 is able to resolve this issue. Upgrading the affected component is advised. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.009 (58.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 58.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.009 · change: +0.004
Affected products
- Cesanta Mongoose — versions 7.0, 7.1, 7.2
Weakness classification (CWE)
References
- vuldb.com/vuln/359528 (technical-description, VDB Entry, Third Party Advisory, vdb-entry)
- vuldb.com/vuln/359528/cti (signature, Permissions Required, permissions-required, VDB Entry)
- vuldb.com/submit/796230 (VDB Entry, Third Party Advisory, third-party-advisory)
- github.com/dwBruijn/CVEs/blob/main/Mongoose/TCP_opt_dos.md (Exploit, Third Party Advisory, exploit)
- github.com/cesanta/mongoose/releases/tag/7.21 (Product, Release Notes, patch)
Frequently asked questions
- What is CVE-2026-6985?
- CVE-2026-6985 is a medium-severity vulnerability in Cesanta Mongoose, classified under Improper Resource Shutdown or Release. CVSS score: 5.3/10. Published 2026-04-25.
- How severe is CVE-2026-6985?
- Medium severity. CVSS v3 base score is 5.3 out of 10.