What is CVE-2019-12951?

CVE-2019-12951 is a critical-severity vulnerability in Cesanta Mongoose, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2019-06-24.

How severe is CVE-2019-12951?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Cesanta Mongoose

CVE-2019-12951

An issue was discovered in Mongoose before 6.15. The parse_mqtt() function in mg_mqtt.c has a critical heap-based buffer overflow.

Vulnerability class: Buffer Overflow

Published 2019-06-24 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.020 (80.1th percentile), scored 2026-10-24.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 80.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.020 · newest: 0.020 · change: 0.000

Affected products

Cesanta Mongoose

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

github.com/cesanta/mongoose/commit/b3e0f780c34cea88f057a62213c012aa88fe2deb (Patch, Third Party Advisory)
github.com/cesanta/mongoose/releases/tag/6.15 (Third Party Advisory, Release Notes)

Frequently asked questions

What is CVE-2019-12951?: CVE-2019-12951 is a critical-severity vulnerability in Cesanta Mongoose, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2019-06-24.
How severe is CVE-2019-12951?: Critical severity. CVSS v3 base score is 9.8 out of 10.