Out-of-bounds Read in Mozilla Firefox
CVE-2026-6784
Memory safety bugs present in Firefox 149 and Thunderbird 149. 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 150 and Thunderbird 150.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.004 (33.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 33.4% 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: 0.004 · change: +0.001
Affected products
- Mozilla Firefox — versions 150
- Mozilla Thunderbird — versions 150
Weakness classification (CWE)
References
- bugzilla.mozilla.org/buglist.cgi
- www.mozilla.org/security/advisories/mfsa2026-30/ (Vendor Advisory)
- www.mozilla.org/security/advisories/mfsa2026-33/ (Vendor Advisory)
- bugzilla.mozilla.org/buglist.cgi
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-6784?
- CVE-2026-6784 is a high-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 7.5/10. Published 2026-04-21.
- How severe is CVE-2026-6784?
- High severity. CVSS v3 base score is 7.5 out of 10.