What is CVE-2019-12206?

CVE-2019-12206 is a critical-severity vulnerability in F5 Njs, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2019-05-20.

How severe is CVE-2019-12206?

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

Buffer overflow in F5 Njs

CVE-2019-12206

njs through 0.3.1, used in NGINX, has a heap-based buffer overflow in nxt_utf8_encode in nxt_utf8.c.

Vulnerability class: Buffer Overflow

Published 2019-05-20 · 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 (79.8th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 80th percentile — 79.8% 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

F5 Njs

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

github.com/nginx/njs/issues/162 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2019-12206?: CVE-2019-12206 is a critical-severity vulnerability in F5 Njs, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2019-05-20.
How severe is CVE-2019-12206?: Critical severity. CVSS v3 base score is 9.8 out of 10.