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Vulnerability details: VCID-61bf-8zpz-vyhz
Vulnerability ID VCID-61bf-8zpz-vyhz
Aliases CVE-2021-23978
Summary Mozilla developers Alexis Beingessner, Tyson Smith, Nika Layzell, and Mats Palmgren reported memory safety bugs present in Thunderbird 78.7. 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-787 Out-of-bounds Write
CWE-120 Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
System Score Found at
cvssv3 8.8 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23978.json
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
epss 0.00754 https://api.first.org/data/v1/epss?cve=CVE-2021-23978
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-2021-23978
cvssv3.1 8.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23978
archlinux High https://security.archlinux.org/AVG-1599
archlinux High https://security.archlinux.org/AVG-1601
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-07
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-08
generic_textual high https://www.mozilla.org/en-US/security/advisories/mfsa2021-09
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23978.json
https://api.first.org/data/v1/epss?cve=CVE-2021-23978
https://bugzilla.mozilla.org/buglist.cgi?bug_id=786797%2C1682928%2C1687391%2C1687597
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23968
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23969
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23973
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23978
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://lists.debian.org/debian-lts-announce/2021/03/msg00000.html
https://security.gentoo.org/glsa/202104-09
https://security.gentoo.org/glsa/202104-10
https://www.debian.org/security/2021/dsa-4866
https://www.mozilla.org/security/advisories/mfsa2021-07/
https://www.mozilla.org/security/advisories/mfsa2021-08/
https://www.mozilla.org/security/advisories/mfsa2021-09/
1932112 https://bugzilla.redhat.com/show_bug.cgi?id=1932112
AVG-1599 https://security.archlinux.org/AVG-1599
AVG-1601 https://security.archlinux.org/AVG-1601
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:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
CVE-2021-23978 https://nvd.nist.gov/vuln/detail/CVE-2021-23978
mfsa2021-07 https://www.mozilla.org/en-US/security/advisories/mfsa2021-07
mfsa2021-08 https://www.mozilla.org/en-US/security/advisories/mfsa2021-08
mfsa2021-09 https://www.mozilla.org/en-US/security/advisories/mfsa2021-09
RHSA-2021:0655 https://access.redhat.com/errata/RHSA-2021:0655
RHSA-2021:0656 https://access.redhat.com/errata/RHSA-2021:0656
RHSA-2021:0657 https://access.redhat.com/errata/RHSA-2021:0657
RHSA-2021:0658 https://access.redhat.com/errata/RHSA-2021:0658
RHSA-2021:0659 https://access.redhat.com/errata/RHSA-2021:0659
RHSA-2021:0660 https://access.redhat.com/errata/RHSA-2021:0660
RHSA-2021:0661 https://access.redhat.com/errata/RHSA-2021:0661
RHSA-2021:0662 https://access.redhat.com/errata/RHSA-2021:0662
USN-4756-1 https://usn.ubuntu.com/4756-1/
USN-4936-1 https://usn.ubuntu.com/4936-1/
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-2021-23978.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-2021-23978
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-2021-23978
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 0.72267
EPSS Score 0.00754
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:47.237516+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-09.yml 37.0.0