CVE-2021-4126 Security feature bypass in Thunderbird
Thunderbird incorrectly validates signatures on nested MIME messages, allowing attackers to spoof signed content and bypass security checks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2021-4126?
CVE-2021-4126 is a medium-severity vulnerability in Mozilla Thunderbird, published on 22 Dec 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
When receiving an OpenPGP/MIME signed email message that contains an additional outer MIME message layer, for example a message footer added by a mailing list gateway, Thunderbird only considered the inner signed message for the signature validity. This gave the false impression that the additional contents were also covered by the digital signature. Starting with Thunderbird version 91.4.1, only the signature that belongs to the top level MIME part will be considered for the displayed status. This vulnerability affects Thunderbird < 91.4.1.
Which versions are affected by CVE-2021-4126?
It affects 1 product.
Products include Mozilla Thunderbird.
How do I fix CVE-2021-4126?
Upgrade to a fixed version.
Is CVE-2021-4126 being exploited?
There is no known exploitation of CVE-2021-4126 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Thunderbird
Sources
Also known as DEBIAN-CVE-2021-4126, GHSA-v2cr-gvw4-g56p, UBUNTU-CVE-2021-4126.