How severe is CVE-2021-23992?

CVE-2021-23992 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2021-23992 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23992?

CVE-2021-23992 affects Mozilla Thunderbird. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-23992?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-23992 published?

CVE-2021-23992 was published on 2021-06-24 and last updated on 2026-06-17.

CVE-2021-23992

CVE-2021-23992 is a medium-severity vulnerability in Mozilla Thunderbird with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-347.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
CVSS v2: 4.3
EPSS exploit prediction: 0% (38th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-347
Affected product: Mozilla Thunderbird
Published: 2021-06-24
Last modified: 2026-06-17

Description

Thunderbird did not check if the user ID associated with an OpenPGP key has a valid self signature. An attacker may create a crafted version of an OpenPGP key, by either replacing the original user ID, or by adding another user ID. If Thunderbird imports and accepts the crafted key, the Thunderbird user may falsely conclude that the false user ID belongs to the correspondent. This vulnerability affects Thunderbird < 78.9.1.

Frequently asked questions

What is CVE-2021-23992?: Thunderbird did not check if the user ID associated with an OpenPGP key has a valid self signature. An attacker may create a crafted version of an OpenPGP key, by either replacing the original user ID, or by adding another user ID. If Thunderbird imports and accepts the crafted key, the Thunderbird user may falsely conclude that the false user ID belongs to the correspondent. This vulnerability affects Thunderbird < 78.9.1.
How severe is CVE-2021-23992?: CVE-2021-23992 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2021-23992 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23992?: CVE-2021-23992 affects Mozilla Thunderbird. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-23992?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-23992 published?: CVE-2021-23992 was published on 2021-06-24 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

More vulnerabilities in Mozilla Thunderbird

CVE-2026-4692 — Critical (CVSS 10.0): Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR…
CVE-2026-4689 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was…
CVE-2026-2778 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in…
CVE-2026-2776 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability…
CVE-2026-2768 — Critical (CVSS 10.0): Sandbox escape in the Storage: IndexedDB component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8,…
CVE-2026-2761 — Critical (CVSS 10.0): Sandbox escape in the Graphics: WebRender component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33,…

All CVEs affecting Mozilla Thunderbird →

Other CWE-347 (Improper Verification of Cryptographic Signature) vulnerabilities

CVE-2026-48558 — Critical (CVSS 10.0): SimpleHelp versions 5.5.15 and prior and 6.0 pre-release versions contain an authentication bypass vulnerability in the…
CVE-2023-25574 — Critical (CVSS 10.0): `jupyterhub-ltiauthenticator` is a JupyterHub authenticator for learning tools interoperability (LTI).…
CVE-2024-45409 — Critical (CVSS 10.0): The Ruby SAML library is for implementing the client side of a SAML authorization. Ruby-SAML in <= 12.2 and 1.13.0 <=…
CVE-2024-32962 — Critical (CVSS 10.0): xml-crypto is an xml digital signature and encryption library for Node.js. In affected versions the default…
CVE-2022-24884 — Critical (CVSS 10.0): ecdsautils is a tiny collection of programs used for ECDSA (keygen, sign, verify). `ecdsa_verify_[prepare_]legacy()`…
CVE-2021-33885 — Critical (CVSS 10.0): An Insufficient Verification of Data Authenticity vulnerability in B. Braun SpaceCom2 prior to 012U000062 allows a…

Browse all CWE-347 (Improper Verification of Cryptographic Signature) vulnerabilities →