What is CVE-2026-0892?

CVE-2026-0892 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2026-01-13.

How severe is CVE-2026-0892?

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

Buffer overflow in Mozilla Firefox

CVE-2026-0892

Memory safety bugs present in Firefox 146 and Thunderbird 146. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 147 and Thunderbird 147.

Vulnerability class: Buffer Overflow

Published 2026-01-13 · 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: 0.005 (37.3th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 37.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.000

Affected products

Mozilla Firefox — versions 147
Mozilla Thunderbird — versions 147

Weakness classification (CWE)

CWE-119 — Improper Restriction of Operations within the Bounds of a Memory Buffer

References

bugzilla.mozilla.org/buglist.cgi (Broken Link)
www.mozilla.org/security/advisories/mfsa2026-01/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-04/ (Vendor Advisory)

Frequently asked questions

What is CVE-2026-0892?: CVE-2026-0892 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2026-01-13.
How severe is CVE-2026-0892?: Critical severity. CVSS v3 base score is 9.8 out of 10.