CVE-2021-23993

MEDIUM
6.5
CVSS Score
Published: June 24, 2021 at 01:26 PM UTC
Updated: June 17, 2026 at 03:39 AM UTC
1 product affected across 1 vendorThunderbird

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.4%

Description

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. This vulnerability affects Thunderbird < 78.9.1.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 78.9.1
Affected range stops below 78.9.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

x_refsource_MISCIssue TrackingPermissions RequiredVendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1666360
x_refsource_MISCRelease NotesVendor Advisory
https://www.mozilla.org/security/advisories/mfsa2021-13/

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
HIGH
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-347

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