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Vulnerability details: VCID-25ev-mwuk-akf2
Vulnerability ID VCID-25ev-mwuk-akf2
Aliases CVE-2021-29976
Summary Mozilla developers Emil Ghitta, Tyson Smith, Valentin Gosu, Olli Pettay, and Randell Jesup reported memory safety bugs present in Firefox 89 and Firefox ESR 78.11. 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 (2)
CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
CWE-787 Out-of-bounds Write
System Score Found at
cvssv3 8.8 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-29976.json
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00252 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00289 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00336 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00336 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00336 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00336 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
epss 0.00336 https://api.first.org/data/v1/epss?cve=CVE-2021-29976
cvssv3.1 8.8 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 6.8 https://nvd.nist.gov/vuln/detail/CVE-2021-29976
cvssv3.1 8.8 https://nvd.nist.gov/vuln/detail/CVE-2021-29976
archlinux High https://security.archlinux.org/AVG-2148
archlinux High https://security.archlinux.org/AVG-2152
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-28
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-29
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-30
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-29976.json
https://api.first.org/data/v1/epss?cve=CVE-2021-29976
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1700895%2C1703334%2C1706910%2C1711576%2C1714391
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29969
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29970
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29976
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-30547
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://security.gentoo.org/glsa/202202-03
https://security.gentoo.org/glsa/202208-14
https://www.mozilla.org/security/advisories/mfsa2021-28/
https://www.mozilla.org/security/advisories/mfsa2021-29/
https://www.mozilla.org/security/advisories/mfsa2021-30/
1982014 https://bugzilla.redhat.com/show_bug.cgi?id=1982014
ASA-202107-20 https://security.archlinux.org/ASA-202107-20
ASA-202107-21 https://security.archlinux.org/ASA-202107-21
AVG-2148 https://security.archlinux.org/AVG-2148
AVG-2152 https://security.archlinux.org/AVG-2152
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-2021-29976 https://nvd.nist.gov/vuln/detail/CVE-2021-29976
mfsa2021-28 https://www.mozilla.org/en-US/security/advisories/mfsa2021-28
mfsa2021-29 https://www.mozilla.org/en-US/security/advisories/mfsa2021-29
mfsa2021-30 https://www.mozilla.org/en-US/security/advisories/mfsa2021-30
RHSA-2021:2740 https://access.redhat.com/errata/RHSA-2021:2740
RHSA-2021:2741 https://access.redhat.com/errata/RHSA-2021:2741
RHSA-2021:2742 https://access.redhat.com/errata/RHSA-2021:2742
RHSA-2021:2743 https://access.redhat.com/errata/RHSA-2021:2743
RHSA-2021:2881 https://access.redhat.com/errata/RHSA-2021:2881
RHSA-2021:2882 https://access.redhat.com/errata/RHSA-2021:2882
RHSA-2021:2883 https://access.redhat.com/errata/RHSA-2021:2883
RHSA-2021:2914 https://access.redhat.com/errata/RHSA-2021:2914
USN-5011-1 https://usn.ubuntu.com/5011-1/
USN-5058-1 https://usn.ubuntu.com/5058-1/
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-2021-29976.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: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-2021-29976
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-2021-29976
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 0.48465
EPSS Score 0.00252
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:45.754385+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-28.yml 37.0.0