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Vulnerability details: VCID-x8nk-sfe2-2qek
Vulnerability ID VCID-x8nk-sfe2-2qek
Aliases CVE-2021-38493
Summary Mozilla developers Tyson Smith and Gabriele Svelto reported memory safety bugs present in Firefox 91 and Firefox ESR 78.13. 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 9.0
Risk 4.5
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-2021-38493.json
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.002 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.00244 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.00244 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.00244 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.00244 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.00244 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
epss 0.00244 https://api.first.org/data/v1/epss?cve=CVE-2021-38493
cvssv3.1 7.5 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 6.8 https://nvd.nist.gov/vuln/detail/CVE-2021-38493
cvssv3.1 8.8 https://nvd.nist.gov/vuln/detail/CVE-2021-38493
archlinux Critical https://security.archlinux.org/AVG-2344
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-38
generic_textual none https://www.mozilla.org/en-US/security/advisories/mfsa2021-39
generic_textual none https://www.mozilla.org/en-US/security/advisories/mfsa2021-42
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-38493.json
https://api.first.org/data/v1/epss?cve=CVE-2021-38493
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1723391%2C1724101%2C1724107
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-38493
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/mfsa2021-39/
https://www.mozilla.org/security/advisories/mfsa2021-42/
2002119 https://bugzilla.redhat.com/show_bug.cgi?id=2002119
AVG-2344 https://security.archlinux.org/AVG-2344
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-2021-38493 https://nvd.nist.gov/vuln/detail/CVE-2021-38493
mfsa2021-38 https://www.mozilla.org/en-US/security/advisories/mfsa2021-38
mfsa2021-39 https://www.mozilla.org/en-US/security/advisories/mfsa2021-39
mfsa2021-42 https://www.mozilla.org/en-US/security/advisories/mfsa2021-42
RHSA-2021:3494 https://access.redhat.com/errata/RHSA-2021:3494
RHSA-2021:3495 https://access.redhat.com/errata/RHSA-2021:3495
RHSA-2021:3496 https://access.redhat.com/errata/RHSA-2021:3496
RHSA-2021:3497 https://access.redhat.com/errata/RHSA-2021:3497
RHSA-2021:3498 https://access.redhat.com/errata/RHSA-2021:3498
RHSA-2021:3499 https://access.redhat.com/errata/RHSA-2021:3499
RHSA-2021:3500 https://access.redhat.com/errata/RHSA-2021:3500
RHSA-2021:3501 https://access.redhat.com/errata/RHSA-2021:3501
USN-5074-1 https://usn.ubuntu.com/5074-1/
USN-5146-1 https://usn.ubuntu.com/5146-1/
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-2021-38493.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:H/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-2021-38493
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-2021-38493
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 0.42465
EPSS Score 0.002
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:47.527949+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-39.yml 37.0.0