What is CVE-2026-2797?

CVE-2026-2797 is a critical-severity vulnerability in Mozilla Firefox, classified under Use After Free. CVSS score: 9.8/10. Published 2026-02-24.

How severe is CVE-2026-2797?

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

Use After Free in Mozilla Firefox

CVE-2026-2797

Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.

Vulnerability class: Use-After-Free

Published 2026-02-24 · last modified 2026-07-15.

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 (38.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 38th percentile — 38.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002

Affected products

Mozilla Firefox — versions 148
Mozilla Thunderbird — versions 148

Weakness classification (CWE)

CWE-416 — Use After Free

References

bugzilla.mozilla.org/show_bug.cgi (Permissions Required)
www.mozilla.org/security/advisories/mfsa2026-13/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-16/ (Vendor Advisory)
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Frequently asked questions

What is CVE-2026-2797?: CVE-2026-2797 is a critical-severity vulnerability in Mozilla Firefox, classified under Use After Free. CVSS score: 9.8/10. Published 2026-02-24.
How severe is CVE-2026-2797?: Critical severity. CVSS v3 base score is 9.8 out of 10.