CVE-2026-6986 Cesanta Mongoose GCM Authentication Tag tls_aes128.c mg_aes_gcm_decrypt signature verification
Remote attackers can bypass GCM authentication tag verification in Cesanta Mongoose, potentially compromising TLS security.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-6986?
CVE-2026-6986 is a medium-severity vulnerability in Cesanta Mongoose, published on 25 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-6986?
It affects 1 product.
Products include Cesanta Mongoose.
How do I fix CVE-2026-6986?
Upgrade to a fixed version.
Is CVE-2026-6986 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-6986 exists.
Other vulnerabilities in Cesanta Mongoose
Sources
Also known as DEBIAN-CVE-2026-6986, GHSA-p5j9-fjff-qrmr, JLSEC-2026-373, UBUNTU-CVE-2026-6986.