CVE-2026-5244 Cesanta Mongoose TLS 1.3 mongoose.c mg_tls_recv_cert heap-based overflow

What is CVE-2026-5244?

CVE-2026-5244 is a medium-severity vulnerability in Cesanta Mongoose, published on 2 Apr 2026.

Official description

A vulnerability has been found in Cesanta Mongoose up to 7.20. This affects the function mg_tls_recv_cert of the file mongoose.c of the component TLS 1.3 Handler. Such manipulation of the argument pubkey leads to heap-based buffer overflow. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 7.21 mitigates this issue. The name of the patch is 0d882f1b43ff2308b7486a56a9d60cd6dba8a3f1. It is advisable to upgrade the affected component. The vendor was contacted early, responded in a very professional manner and quickly released a fixed version of the affected product.

Weakness: CWE-122, CWE-119

Which versions are affected by CVE-2026-5244?

It affects 1 product.

Products include Cesanta Mongoose.

How do I fix CVE-2026-5244?

Upgrade to a fixed version.

Is CVE-2026-5244 being exploited?

There is no known exploitation of CVE-2026-5244 in the wild and no public exploit code.

Other vulnerabilities in Cesanta Mongoose

• CVE-2022-25299 Arbitrary File Write Critical 9.8
• CVE-2020-25756 Memory corruption in n/a Critical 9.8
• CVE-2019-19307 Integer overflow in n/a Critical 9.8
• CVE-2019-12951 Memory corruption in n/a Critical 9.8
• CVE-2018-20353 Use after free in n/a Critical 9.8

All Cesanta Mongoose vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-5244, GHSA-7vfw-f3r2-9m2j, JLSEC-2026-369, UBUNTU-CVE-2026-5244.