What is CVE-2026-8973?

CVE-2026-8973 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 8.8/10. Published 2026-05-19.

How severe is CVE-2026-8973?

High severity. CVSS v3 base score is 8.8 out of 10.

Buffer overflow in Mozilla Firefox

CVE-2026-8973

Memory safety bugs present in Firefox 150. 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 151 and Thunderbird 151.

Vulnerability class: Buffer Overflow

Published 2026-05-19 · last modified 2026-07-23.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.005 (37.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 37.2% 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: +0.001

Affected products

Mozilla Firefox — versions 151
Mozilla Thunderbird — versions 151

Weakness classification (CWE)

References

bugzilla.mozilla.org/buglist.cgi (Broken Link)
www.mozilla.org/security/advisories/mfsa2026-46/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2026-50/ (Vendor Advisory)
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Frequently asked questions

What is CVE-2026-8973?: CVE-2026-8973 is a high-severity vulnerability in Mozilla Firefox, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 8.8/10. Published 2026-05-19.
How severe is CVE-2026-8973?: High severity. CVSS v3 base score is 8.8 out of 10.