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Vulnerability details: VCID-bkrp-7kf2-b7er
Vulnerability ID VCID-bkrp-7kf2-b7er
Aliases CVE-2021-23959
Summary An XSS bug in internal error pages could have led to various spoofing attacks, including other error pages and the address bar.*Note: This issue 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-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
System Score Found at
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
epss 0.00302 https://api.first.org/data/v1/epss?cve=CVE-2021-23959
cvssv2 4.3 https://nvd.nist.gov/vuln/detail/CVE-2021-23959
cvssv3.1 6.1 https://nvd.nist.gov/vuln/detail/CVE-2021-23959
archlinux Medium https://security.archlinux.org/AVG-1493
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-03
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-23959
https://bugzilla.mozilla.org/show_bug.cgi?id=1659035
https://www.mozilla.org/security/advisories/mfsa2021-03/
AVG-1493 https://security.archlinux.org/AVG-1493
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-2021-23959 https://nvd.nist.gov/vuln/detail/CVE-2021-23959
mfsa2021-03 https://www.mozilla.org/en-US/security/advisories/mfsa2021-03
No exploits are available.
Vector: AV:N/AC:M/Au:N/C:N/I:P/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23959
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:C/C:L/I:L/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23959
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 0.53089
EPSS Score 0.00302
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:50.422456+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-03.yml 37.0.0