What is CVE-2019-9805?

CVE-2019-9805 is a critical-severity vulnerability in Mozilla Firefox, classified under Use of Uninitialized Resource. CVSS score: 9.8/10. Published 2019-04-26.

How severe is CVE-2019-9805?

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

Vulnerability in Mozilla Firefox

CVE-2019-9805

A latent vulnerability exists in the Prio library where data may be read from uninitialized memory for some functions, leading to potential memory corruption. This vulnerability affects Firefox < 66.

Published 2019-04-26 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.014 (71.5th percentile), scored 2026-10-25.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

Mozilla Firefox — versions unspecified

Weakness classification (CWE)

CWE-908 — Use of Uninitialized Resource

References

www.mozilla.org/security/advisories/mfsa2019-07/ (Vendor Advisory)
bugzilla.mozilla.org/show_bug.cgi (Issue Tracking, Vendor Advisory)

Frequently asked questions

What is CVE-2019-9805?: CVE-2019-9805 is a critical-severity vulnerability in Mozilla Firefox, classified under Use of Uninitialized Resource. CVSS score: 9.8/10. Published 2019-04-26.
How severe is CVE-2019-9805?: Critical severity. CVSS v3 base score is 9.8 out of 10.