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CVE-2021-23977

Firefox for Android suffered from a time-of-check-time-of-use vulnerability that allowed a...

5.3 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.88%Up 0.3 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used5.3

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.

Record
CVE-2021-23977
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
CVSS 2.0
2.6 LowAV:N/AC:H/Au:N/C:P/I:N/A:N
Weakness
CWE-367
Updated
2026-11-02
CVE ListNo score

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.

Record
CVE-2021-23977
Updated
2026-11-02
EUVDEUVD-2021-10898No score

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.

Record
EUVD-2021-10898
Updated
2026-11-03
GitHub AdvisoriesGHSA-cc5x-973x-6p4m5.3

Firefox for Android suffered from a time-of-check-time-of-use vulnerability that allowed a...

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.

Record
GHSA-cc5x-973x-6p4m
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Weakness
CWE-367
Updated
2026-11-02
OSVALPINE-CVE-2021-239775.3

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.

Record
ALPINE-CVE-2021-23977
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Updated
2026-11-03
OSVUBUNTU-CVE-2021-239775.3

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.

Record
UBUNTU-CVE-2021-23977
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVopenSUSE-SU-2024:10600-1No score

MozillaFirefox-92.0-1.2 on GA media

These are all security issues fixed in the MozillaFirefox-92.0-1.2 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:10600-1
Updated
2026-11-02
OSVopenSUSE-SU-2024:14572-1No score

firefox-esr-128.5.1-1.1 on GA media

These are all security issues fixed in the firefox-esr-128.5.1-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:14572-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
firefox
Alpine:v3.13
before 87.0-r0
87.0-r0
firefox
Alpine:v3.14
before 87.0-r0
87.0-r0
firefox
Alpine:v3.15
before 87.0-r0
87.0-r0
firefox
Alpine:v3.16
before 87.0-r0
87.0-r0
firefox
Alpine:v3.17
before 87.0-r0
87.0-r0
firefox
Alpine:v3.18
before 87.0-r0
87.0-r0
firefox
Alpine:v3.19
before 87.0-r0
87.0-r0
firefox
Alpine:v3.20
before 87.0-r0
87.0-r0
firefox
Alpine:v3.21
before 87.0-r0
87.0-r0
firefox
Alpine:v3.22
before 87.0-r0
87.0-r0
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Affected packages
PackageAffectedFixed
firefox
Alpine:v3.23
before 87.0-r0
87.0-r0
librewolf
Alpine:v3.21
before 87.0-r0
87.0-r0
librewolf
Alpine:v3.22
before 87.0-r0
87.0-r0
librewolf
Alpine:v3.23
before 87.0-r0
87.0-r0
librewolf
Alpine:v3.24
before 87.0-r0
87.0-r0
mozjs52
Ubuntu:18.04:LTS
All versions, plus listed versions
52.3.1-0ubuntu352.3.1-7fakesync152.8.1-0ubuntu0.18.04.152.9.1-0ubuntu0.18.04.1
None known
mozjs38
Ubuntu:18.04:LTS
All versions, plus listed versions
38.8.0~repack1-0ubuntu138.8.0~repack1-0ubuntu338.8.0~repack1-0ubuntu4
None known
mozjs68
Ubuntu:20.04:LTS
All versions, plus listed versions
68.5.0-1~fakesync68.5.0-2~fakesync68.6.0-168.6.0-1ubuntu1
None known
mozjs52
Ubuntu:20.04:LTS
All versions, plus listed versions
52.9.1-1build152.9.1-1ubuntu3
None known
mozjs78
Ubuntu:22.04:LTS
All versions, plus listed versions
78.13.0-178.15.0-278.15.0-4ubuntu1
None known
MozillaFirefox
openSUSE:Tumbleweed
From an advisory covering 661 CVEs
before 92.0-1.2
92.0-1.2
firefox-esr
openSUSE:Tumbleweed
From an advisory covering 1860 CVEs
before 128.5.1-1.1
128.5.1-1.1

History

History
RecordedChangedSources
affected, facts
affected, aliases, referencesOSV
aliasesEUVD
first indexedCVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-23977 is a medium vulnerability (CVSS 5.3) in Mozilla Firefox, published February 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.88%, the 59th percentile. Fixed in firefox 87.0-r0.

References

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