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CVE-2021-23968

18
FAUCET Score

CVE-2021-23968 is a medium-severity information disclosure vulnerability affecting Firefox, Thunderbird, and Firefox ESR versions prior to 86 and 78.8 respectively. It allowed Content Security Policy (CSP) violation reports to inadvertently leak the full destination of redirected frame navigations, rather than just the original URI, potentially exposing sensitive information. The attack requires user interaction (UI:R) and has a low impact on confidentiality (C:L). There is no evidence of active exploitation, publicly available exploit code, or significant community discussion, and it is not listed in CISA's KEV catalog.

Impacted Technologies

VendorProductVersion(s)CPE
< 86.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 78.8CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
< 78.8CPE matchmatch criteria
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

4.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.21%
Probability of exploitation in next 30 days
EPSS Percentile
65.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0121 is in the 78th percentile among its peer group of 26,236 CVEs.

Social Chatter

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

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 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-0:78.8.0-1.el8_2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:78.8.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: thunderbird-0:78.8.0-1.el7_9
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: firefox-0:78.8.0-1.el8_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: thunderbird-0:78.8.0-1.el8_3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: thunderbird-0:78.8.0-1.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: firefox-0:78.8.0-1.el8_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: firefox-0:78.8.0-1.el8_2
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2021-23968Important

Mozilla: Content Security Policy violation report could have contained the destination of a redirect

Feb 23, 2021

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions RequiredVendor Advisory
lists.debian.org / debian-lts-announce/2021/03/msg00000.html
Mailing ListThird Party Advisory
security.gentoo.org / glsa/202104-09
Third Party Advisory
security.gentoo.org / glsa/202104-10
Third Party Advisory
debian.org / security/2021/dsa-4866
Third Party Advisory
mozilla.org / security/advisories/mfsa2021-07
Release NotesVendor Advisory
mozilla.org / security/advisories/mfsa2021-08
Release NotesVendor Advisory
mozilla.org / security/advisories/mfsa2021-09
Release NotesVendor Advisory