Vulnerability · Published Apr 25, 2026 · Assigned by VulDB
CVE-2026-6986Cesanta Mongoose GCM Authentication Tag tls_aes128.c mg_aes_gcm_decrypt signature verification
Low 3.7
In plain English
A low-severity insufficient verification of data authenticity in Mongoose from Cesanta. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | swupdate | no fix listed | DEBIAN-CVE-2026-6986 |
| Debian:13 | swupdate | no fix listed | DEBIAN-CVE-2026-6986 |
| Debian:14 | swupdate | 2025.12+dfsg-10 | DEBIAN-CVE-2026-6986 |
| Ubuntu:22.04:LTS | swupdate | no fix listed | UBUNTU-CVE-2026-6986 |
| Ubuntu:24.04:LTS | swupdate | no fix listed | UBUNTU-CVE-2026-6986 |
| Ubuntu:25.10 | swupdate | no fix listed | UBUNTU-CVE-2026-6986 |
| Ubuntu:26.04:LTS | swupdate | no fix listed | UBUNTU-CVE-2026-6986 |
| Ubuntu:26.10 | swupdate | no fix listed | UBUNTU-CVE-2026-6986 |
Affected products (as reported)
Weakness: CWE-347, CWE-345 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:O/RC:C
References
- VDB-359529 | Cesanta Mongoose GCM Authentication Tag tls_aes128.c mg_aes_gcm_decrypt signature verification vdb-entry, technical-description
- VDB-359529 | CTI Indicators (IOB, IOC, IOA) signature, permissions-required
- Submit #796231 | Cesanta Mongoose 7.20 Improper Verification of Cryptographic Signature third-party-advisory
- https://github.com/dwBruijn/CVEs/blob/main/Mongoose/AESGCM.md exploit
- https://github.com/cesanta/mongoose/releases/tag/7.21 patch