CVE-2021-23991 Denial of service in Thunderbird
An attacker can prevent encrypted email delivery to a recipient by exploiting invalid subkey handling in Thunderbird's OpenPGP implementation.
- 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-2021-23991?
CVE-2021-23991 is a medium-severity denial of service vulnerability in Mozilla Thunderbird, published on 24 Jun 2021. 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
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.
Which versions are affected by CVE-2021-23991?
It affects 1 product.
Products include Mozilla Thunderbird.
How do I fix CVE-2021-23991?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2021-23991 being exploited?
There is no known exploitation of CVE-2021-23991 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Thunderbird
Sources
Also known as DEBIAN-CVE-2021-23991, GHSA-x5j6-p8w8-5r65, UBUNTU-CVE-2021-23991.