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Vulnerability details: VCID-js1d-a4rb-mkg1
Vulnerability ID VCID-js1d-a4rb-mkg1
Aliases CVE-2021-23991
Summary If a Thunderbird user has previously imported Alice's OpenPGP key, and Alice has extended the validity period of her key, but Alice's updated key has not yet been imported, an attacker may send an email containing a crafted version of Alice's key with an invalid subkey, Thunderbird might subsequently attempt to use the invalid subkey, and will fail to send encrypted email to Alice.
Status Published
Exploitability 0.5
Weighted Severity 6.2
Risk 3.1
Affected and Fixed Packages Package Details
Weaknesses (1)
CWE-347 Improper Verification of Cryptographic Signature
System Score Found at
cvssv3 6.8 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23991.json
epss 0.00204 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
epss 0.00217 https://api.first.org/data/v1/epss?cve=CVE-2021-23991
cvssv3.1 4.3 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 4.0 https://nvd.nist.gov/vuln/detail/CVE-2021-23991
cvssv3.1 6.8 https://nvd.nist.gov/vuln/detail/CVE-2021-23991
archlinux Medium https://security.archlinux.org/AVG-1790
generic_textual none https://www.mozilla.org/en-US/security/advisories/mfsa2021-13
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23991.json
https://api.first.org/data/v1/epss?cve=CVE-2021-23991
https://bugzilla.mozilla.org/show_bug.cgi?id=1673240
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23961
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23991
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23992
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23993
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23994
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23995
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23998
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23999
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-24002
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29945
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29946
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29948
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29949
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://www.mozilla.org/security/advisories/mfsa2021-13/
1948393 https://bugzilla.redhat.com/show_bug.cgi?id=1948393
AVG-1790 https://security.archlinux.org/AVG-1790
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-2021-23991 https://nvd.nist.gov/vuln/detail/CVE-2021-23991
mfsa2021-13 https://www.mozilla.org/en-US/security/advisories/mfsa2021-13
RHSA-2021:1190 https://access.redhat.com/errata/RHSA-2021:1190
RHSA-2021:1192 https://access.redhat.com/errata/RHSA-2021:1192
RHSA-2021:1193 https://access.redhat.com/errata/RHSA-2021:1193
RHSA-2021:1201 https://access.redhat.com/errata/RHSA-2021:1201
USN-4995-1 https://usn.ubuntu.com/4995-1/
USN-4995-2 https://usn.ubuntu.com/4995-2/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23991.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:N/I:N/A:L 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:H/Au:N/C:P/I:P/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23991
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:H/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23991
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 0.4284
EPSS Score 0.00204
Published At Aug. 16, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:48.195079+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-13.yml 37.0.0