What is CVE-2026-6986?

CVE-2026-6986 is a low-severity vulnerability in Cesanta Mongoose, classified under Insufficient Verification of Data Authenticity. CVSS score: 3.7/10. Published 2026-04-25.

How severe is CVE-2026-6986?

Low severity. CVSS v3 base score is 3.7 out of 10.

Vulnerability in Cesanta Mongoose

CVE-2026-6986

A security vulnerability has been detected in Cesanta Mongoose up to 7.20. This issue affects the function mg_aes_gcm_decrypt of the file /src/tls_aes128.c of the component GCM Authentication Tag Handler. Such manipulation leads to improper verification of cryptographic signature. The attack may be performed from remote. A high complexity level is associated with this attack. The exploitability is assessed as difficult. The exploit has been disclosed publicly and may be used. Upgrading to version 7.21 is capable of addressing this issue. It is advisable to upgrade the affected component. VulDB has contacted the vendor early and they confirmed quickly, that this issue got fixed already.

Published 2026-04-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (15.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000

Affected products

Cesanta Mongoose — versions 7.0, 7.1, 7.2

Weakness classification (CWE)

References

vuldb.com/vuln/359529 (technical-description, VDB Entry, Third Party Advisory, vdb-entry)
vuldb.com/vuln/359529/cti (signature, Permissions Required, permissions-required, VDB Entry)
vuldb.com/submit/796231 (VDB Entry, Third Party Advisory, third-party-advisory)
github.com/dwBruijn/CVEs/blob/main/Mongoose/AESGCM.md (Exploit, Third Party Advisory, exploit)
github.com/cesanta/mongoose/releases/tag/7.21 (Release Notes, patch)

Frequently asked questions

What is CVE-2026-6986?: CVE-2026-6986 is a low-severity vulnerability in Cesanta Mongoose, classified under Insufficient Verification of Data Authenticity. CVSS score: 3.7/10. Published 2026-04-25.
How severe is CVE-2026-6986?: Low severity. CVSS v3 base score is 3.7 out of 10.