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Vulnerability details: VCID-ync5-k23g-kfg7
Vulnerability ID VCID-ync5-k23g-kfg7
Aliases CVE-2021-23993
Summary An attacker may perform a DoS attack to prevent a user from sending encrypted email to a correspondent. If an attacker creates a crafted OpenPGP key with a subkey that has an invalid self signature, and the Thunderbird user imports the crafted key, then Thunderbird may try to use the invalid subkey, but the RNP library rejects it from being used, causing encryption to fail.
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 6.5 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23993.json
epss 0.00051 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
epss 0.00054 https://api.first.org/data/v1/epss?cve=CVE-2021-23993
cvssv3.1 4.3 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 4.3 https://nvd.nist.gov/vuln/detail/CVE-2021-23993
cvssv3.1 6.5 https://nvd.nist.gov/vuln/detail/CVE-2021-23993
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-2021-23993.json
https://api.first.org/data/v1/epss?cve=CVE-2021-23993
https://bugzilla.mozilla.org/show_bug.cgi?id=1666360
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/
1948395 https://bugzilla.redhat.com/show_bug.cgi?id=1948395
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-2021-23993 https://nvd.nist.gov/vuln/detail/CVE-2021-23993
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:L/PR:N/UI:R/S:U/C:N/I:H/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2021-23993.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:M/Au:N/C:N/I:P/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23993
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:N/I:H/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-23993
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 0.15519
EPSS Score 0.00051
Published At Aug. 16, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:48.243625+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2021/mfsa2021-13.yml 37.0.0