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CVE-2021-23977

20
FAUCET Score

CVE-2021-23977 is a time-of-check-time-of-use (TOCTOU) vulnerability in Firefox for Android versions prior to 86, allowing malicious applications to read sensitive data from Firefox's directories. Rated Medium (CVSS 5.3), it requires user interaction and high attack complexity, but could lead to high confidentiality impact. There is no evidence of active exploitation, public exploit code, or significant community attention, with only one article and one mention identified.

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

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
NONE
Exploitability Score
1.6
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.87%
Probability of exploitation in next 30 days
EPSS Percentile
55.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0087 is in the 69th percentile among its peer group of 707 CVEs.

Social Chatter

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

Media Mentions

The average CVE in this peer group has 0.2 InfoSec Media, 0.0 Vendor Blog, and 0.0 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