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Vulnerability details: VCID-zuh2-7wkb-d7f9
Vulnerability ID VCID-zuh2-7wkb-d7f9
Aliases CVE-2021-23960
Summary Performing garbage collection on re-declared JavaScript variables resulted in a user-after-poison, and a potentially exploitable crash.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-626 Null Byte Interaction Error (Poison Null Byte)
System Score Found at
cvssv3 8.8 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23960.json
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
epss 0.00421 https://api.first.org/data/v1/epss?cve=CVE-2021-23960
cvssv3.1 6.1 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 6.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23960
cvssv3.1 8.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23960
archlinux High https://security.archlinux.org/AVG-1492
archlinux High https://security.archlinux.org/AVG-1496
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-03
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-04
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-05
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23960.json
https://api.first.org/data/v1/epss?cve=CVE-2021-23960
https://bugzilla.mozilla.org/show_bug.cgi?id=1675755
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15685
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-16044
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-26976
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23953
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23954
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23960
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23964
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://www.mozilla.org/security/advisories/mfsa2021-03/
https://www.mozilla.org/security/advisories/mfsa2021-04/
1920650 https://bugzilla.redhat.com/show_bug.cgi?id=1920650
ASA-202102-1 https://security.archlinux.org/ASA-202102-1
ASA-202102-2 https://security.archlinux.org/ASA-202102-2
AVG-1492 https://security.archlinux.org/AVG-1492
AVG-1496 https://security.archlinux.org/AVG-1496
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
CVE-2021-23960 https://nvd.nist.gov/vuln/detail/CVE-2021-23960
mfsa2021-03 https://www.mozilla.org/en-US/security/advisories/mfsa2021-03
mfsa2021-04 https://www.mozilla.org/en-US/security/advisories/mfsa2021-04
mfsa2021-05 https://www.mozilla.org/en-US/security/advisories/mfsa2021-05
RHSA-2021:0285 https://access.redhat.com/errata/RHSA-2021:0285
RHSA-2021:0288 https://access.redhat.com/errata/RHSA-2021:0288
RHSA-2021:0289 https://access.redhat.com/errata/RHSA-2021:0289
RHSA-2021:0290 https://access.redhat.com/errata/RHSA-2021:0290
RHSA-2021:0297 https://access.redhat.com/errata/RHSA-2021:0297
RHSA-2021:0298 https://access.redhat.com/errata/RHSA-2021:0298
RHSA-2021:0299 https://access.redhat.com/errata/RHSA-2021:0299
RHSA-2021:0397 https://access.redhat.com/errata/RHSA-2021:0397
USN-4717-1 https://usn.ubuntu.com/4717-1/
USN-4736-1 https://usn.ubuntu.com/4736-1/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23960.json
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: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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:P Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23960
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:H Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23960
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 0.61129
EPSS Score 0.00421
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:50.261551+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-04.yml 37.0.0