What is CVE-2020-6800?

CVE-2020-6800 is a high-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Write. CVSS score: 8.8/10. Published 2020-03-02.

How severe is CVE-2020-6800?

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

Buffer overflow in Mozilla Firefox

CVE-2020-6800

Mozilla developers and community members reported memory safety bugs present in Firefox 72 and Firefox ESR 68.4. 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. In general, these flaws cannot be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or browser-like contexts. This vulnerability affects Thunderbird < 68.5, Firefox < 73, and Firefox < ESR68.5.

Vulnerability class: Buffer Overflow

Published 2020-03-02 · last modified 2026-06-17.

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: 0.024 (83.1th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 83rd percentile — 83.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.023 · newest: 0.024 · change: +0.001

Affected products

Mozilla Firefox — versions unspecified
Mozilla Firefox Esr
Mozilla Thunderbird — versions unspecified
Canonical Ubuntu Linux — versions 16.04, 18.04, 19.10

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

www.mozilla.org/security/advisories/mfsa2020-05/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2020-06/ (Vendor Advisory)
www.mozilla.org/security/advisories/mfsa2020-07/ (Vendor Advisory)
bugzilla.mozilla.org/buglist.cgi (Issue Tracking, Broken Link)
usn.ubuntu.com/4278-2/ (vendor-advisory, Third Party Advisory)
security.gentoo.org/glsa/202003-02 (vendor-advisory, Third Party Advisory)
security.gentoo.org/glsa/202003-10 (vendor-advisory, Third Party Advisory)
usn.ubuntu.com/4328-1/ (vendor-advisory, Third Party Advisory)
usn.ubuntu.com/4335-1/ (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2020-6800?: CVE-2020-6800 is a high-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Write. CVSS score: 8.8/10. Published 2020-03-02.
How severe is CVE-2020-6800?: High severity. CVSS v3 base score is 8.8 out of 10.