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CVE-2021-23964

26
FAUCET Score

CVE-2021-23964 describes multiple memory safety bugs in Mozilla Firefox, Firefox ESR, and Thunderbird versions prior to 85, 78.7, and 78.7 respectively. These vulnerabilities, rated 8.8 HIGH, could lead to arbitrary code execution due to memory corruption, requiring user interaction for exploitation over a network. While no active exploitation or public exploit code is known, the potential for high impact on confidentiality, integrity, and availability is significant. Community discussion and media coverage are minimal, suggesting low public awareness despite the high severity.

Impacted Technologies

VendorProductVersion(s)CPE
< 85.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 78.7CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
< 78.7CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.8HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.26%
Probability of exploitation in next 30 days
EPSS Percentile
66.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0126 is in the 65th percentile among its peer group of 14,875 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.2 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.1 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (9)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: thunderbird-0:78.7.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:78.7.0-2.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: thunderbird-0:78.7.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:78.7.0-2.el8_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:78.7.0-1.el8_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: firefox-0:78.7.0-2.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: thunderbird-0:78.7.0-1.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: firefox-0:78.7.0-2.el8_2
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2021-23964Important

Mozilla: Memory safety bugs fixed in Firefox 85 and Firefox ESR 78.7

Jan 26, 2021

References

bugzilla.mozilla.org / buglist.cgi
Broken LinkIssue TrackingVendor Advisory
mozilla.org / security/advisories/mfsa2021-03
Release NotesVendor Advisory
mozilla.org / security/advisories/mfsa2021-04
Release NotesVendor Advisory
mozilla.org / security/advisories/mfsa2021-05
Release NotesVendor Advisory