Vulnerability identifier: #VU52002

Vulnerability risk: Low

CVSSv3.1: 3.7 [CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-23991

CWE-ID: CWE-310

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Mozilla Thunderbird
Client/Desktop applications / Messaging software

Vendor: Mozilla

Description

The vulnerability allows a remote attacker to email encryption.

The vulnerability exists in the way Thunderbird uses the OpenPGP key refresh mechanism while handling the extended validity key period. A remote attacker can send  victim an email containing a crafted version of the original key and an invalid subkey and force the application to use the invalid subkey, which will result in failure to encrypt the original email message when sending it.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Mozilla Thunderbird: 78.0 - 78.9.0, 68.0 - 68.12.1, 60.0 - 60.9.1

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External links
http://www.mozilla.org/en-US/security/advisories/mfsa2021-13/

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.