Firefox for Android suffered from a time-of-check-time-of-use vulnerability that allowed a malicious application to read sensitive data fro…

published 2021-02-26 5y ago modified 2026-06-17 4mo ago also EUVD-2021-10898

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 59%
public exploits: 0; none known

Firefox for Android suffered from a time-of-check-time-of-use vulnerability that allowed a malicious application to read sensitive data from application directories. Note: This issue is only affected Firefox for Android. Other operating systems are unaffected. This vulnerability affects Firefox < 86.

Patch / fix

fixed in 1 distros 2

mozilla firefox 86.0

opensuse alpine

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

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

firefox Alpine 3.23, Alpine 3.22, Alpine 3.21 +8 more 87.0-r0
librewolf Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 87.0-r0

alpine advisories ALPINE-CVE-2021-23977

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

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Exploit prediction

0.88% chance of exploitation in the next 30 days, higher than 59% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
NVD	2.0	2.6	AV:N/AC:H/Au:N/C:P/I:N/A:N

Affected products

Mozilla Firefox

Classification

Weakness

CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

security.gentoo.org /glsa/202104-10
vendor-advisory, third-party-advisory
mozilla.org /security/advisories/mfsa2021-07/
release-notes, vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1684761
issue-tracking, permissions-required, vendor-advisory

Sources

CVE List CVE-2021-23977
NVD CVE-2021-23977

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