Is CVE-2021-23991 in the CISA KEV catalog?

No. CVE-2021-23991 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-23991?

CVE-2021-23991 has a CVSS v3 base score of 6.8 (MEDIUM).

What is the EPSS score for CVE-2021-23991?

CVE-2021-23991 has an EPSS score of 1.03% (60th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-23991?

Upgrade thunderbird on debian 11 to 1:78.10.0-1 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2021-23991

MEDIUM

6.8

CVSS v3

NVD

Description

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. This vulnerability affects Thunderbird < 78.9.1.

How to fix

Remediation Available

thunderbirdDebian

Fixed in:1:78.10.0-1CVE-2021-23991

thunderbirdUbuntu

Fixed in:1:78.11.0+build1-0ubuntu0.18.04.2USN-4995-2

Fixed in:1:78.11.0+build1-0ubuntu0.20.04.2USN-4995-1

Mozilla Thunderbird (en-US)Windows application

Affected:78.9.1Fixed in:78.9.1Mozilla

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionRequired

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

Exploit Intelligence

1.03%probability of exploitation in 30 days

60thpercentile

Moderate risk: more likely to be exploited than 60% of all known CVEs.

References

Exploit1

bugzilla.mozilla.org

Vendor Advisory1

mozilla.org

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.