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Vulnerability details: VCID-cf28-37ns-xqdt
Vulnerability ID VCID-cf28-37ns-xqdt
Aliases CVE-2021-23979
Summary Mozilla developers Tyson Smith, Lars T Hansen, Valentin Gosu, and Sebastian Hengst reported memory safety bugs present in Firefox 85. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-787 Out-of-bounds Write
System Score Found at
epss 0.0034 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.0034 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.0034 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.0034 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.0034 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.0034 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
epss 0.00374 https://api.first.org/data/v1/epss?cve=CVE-2021-23979
cvssv3.1 8.1 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 6.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23979
cvssv3.1 8.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23979
archlinux High https://security.archlinux.org/AVG-1599
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-2021-23979
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1663222%2C1666607%2C1672120%2C1678463%2C1678927%2C1679560%2C1681297%2C1681684%2C1683490%2C1684377%2C1684902
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://www.mozilla.org/security/advisories/mfsa2021-07/
AVG-1599 https://security.archlinux.org/AVG-1599
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:*:*:*:*:*:*:*:*
CVE-2021-23979 https://nvd.nist.gov/vuln/detail/CVE-2021-23979
mfsa2021-07 https://www.mozilla.org/en-US/security/advisories/mfsa2021-07
USN-4756-1 https://usn.ubuntu.com/4756-1/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H 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-2021-23979
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-2021-23979
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 0.56102
EPSS Score 0.0034
Published At Sept. 16, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:48.921573+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-07.yml 37.0.0