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Vulnerability details: VCID-3y8m-vwcb-27b2
Vulnerability ID VCID-3y8m-vwcb-27b2
Aliases CVE-2021-23976
Summary When accepting a malicious intent from other installed apps, Firefox for Android accepted manifests from arbitrary file paths and allowed declaring webapp manifests for other origins. This could be used to gain fullscreen access for UI spoofing and could also lead to cross-origin attacks on targeted websites.*Note: This issue is a different issue from CVE-2020-26954 and only affected Firefox for Android. Other operating systems are unaffected.*
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-1021 Improper Restriction of Rendered UI Layers or Frames
System Score Found at
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
epss 0.00334 https://api.first.org/data/v1/epss?cve=CVE-2021-23976
cvssv3.1 6.3 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 5.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23976
cvssv3.1 8.1 https://nvd.nist.gov/vuln/detail/CVE-2021-23976
archlinux Medium https://security.archlinux.org/AVG-1600
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-07
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-23976
https://bugzilla.mozilla.org/show_bug.cgi?id=1684627
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://security.gentoo.org/glsa/202104-10
https://www.mozilla.org/security/advisories/mfsa2021-07/
AVG-1600 https://security.archlinux.org/AVG-1600
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:android:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:mozilla:firefox:*:*:*:*:*:android:*:*
CVE-2021-23976 https://nvd.nist.gov/vuln/detail/CVE-2021-23976
mfsa2021-07 https://www.mozilla.org/en-US/security/advisories/mfsa2021-07
No exploits are available.
Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: AV:N/AC:M/Au:N/C:P/I:P/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23976
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23976
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.55572
EPSS Score 0.00334
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:48.807672+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-07.yml 37.0.0