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CVE-2021-23976

26
FAUCET Score

CVE-2021-23976 is a high-severity vulnerability affecting Firefox for Android versions prior to 86. It allowed malicious Android applications to provide arbitrary webapp manifests, leading to UI spoofing through fullscreen access and potential cross-origin attacks. The vulnerability has a CVSS score of 8.1, indicating a high impact on confidentiality and integrity with low attack complexity, requiring user interaction. While not listed in CISA's KEV catalog and lacking public exploit code, it has garnered some community discussion and media coverage, suggesting awareness of its potential.

Impacted Technologies

VendorProductVersion(s)CPE
< 86.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:android:*:*

CVSS Data

CVSS version used by this source: 3.1

8.1HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.10%
Probability of exploitation in next 30 days
EPSS Percentile
62.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0110 is in the 61st 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

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingPermissions RequiredVendor Advisory
security.gentoo.org / glsa/202104-10
Third Party Advisory
mozilla.org / security/advisories/mfsa2021-07
Release NotesVendor Advisory