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Fencer Vulns
critical 9.8

CVE-2020-6815 json

Mozilla developers reported memory safety and script safety bugs present in Firefox 73.

published 2020-03-25 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-27961

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 71%
public exploits
0
none known

Summary

Mozilla developers reported memory safety and script safety bugs present in Firefox 73. Some of these bugs showed evidence of memory corruption or escalation of privilege and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 74.

Patch / fix

  • Mozilla Firefox 74
  • firefox Ubuntu 16.04 LTS 74.0+build3-0ubuntu0.16.04.1
  • firefox Ubuntu 18.04 LTS 74.0+build3-0ubuntu0.18.04.1
  • firefox Ubuntu 20.04 LTS 74.0+build3-0ubuntu1

ubuntu advisories UBUNTU-CVE-2020-6815

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox-esr openSUSE Tumbleweed 128.5.1-1.1
  • MozillaFirefox openSUSE Tumbleweed 92.0-1.2

opensuse advisories openSUSE-SU-2024:14572-1openSUSE-SU-2024:10600-1

  • firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +9 more 74.0-r0
  • librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 74.0-r0

alpine advisories ALPINE-CVE-2020-6815

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • firefox Arch Linux 74.0-1
  • thunderbird Arch Linux 68.7.0-1

arch linux advisories AVG-1112AVG-1132

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-6815 updated cvss 9.8

Mozilla: Memory and script safety bugs fixed in Firefox 74

  • Red Hat Enterprise Linux 5 firefox
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 6 firefox Red Hat Enterprise Linux 7 firefox Red Hat Enterprise Linux 8 firefox
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.36% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected products

  • Mozilla Firefox

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.