What is CVE-2026-0889?

CVE-2026-0889 is a high-severity vulnerability in Mozilla Firefox, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-01-13.

How severe is CVE-2026-0889?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Mozilla Firefox

CVE-2026-0889

Denial-of-service in the DOM: Service Workers component. This vulnerability was fixed in Firefox 147 and Thunderbird 147.

Vulnerability class: DoS (Denial of Service)

Published 2026-01-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.006 (46.8th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 46.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: +0.000

Affected products

Mozilla Firefox — versions 147
Mozilla Thunderbird — versions 147

Weakness classification (CWE)

CWE-400 — Uncontrolled Resource Consumption

References

bugzilla.mozilla.org/show_bug.cgi (Exploit, Issue Tracking, Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-01/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-04/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-0889?: CVE-2026-0889 is a high-severity vulnerability in Mozilla Firefox, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-01-13.
How severe is CVE-2026-0889?: High severity. CVSS v3 base score is 7.5 out of 10.