CVE-2021-4126

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.

6.5

CVSS

Severity: Medium

CVSS 3.1 •

EPSS 0.12%

Vendor Advisory mozilla.org Vendor Advisory mozilla.org

Affected: Mozilla Thunderbird

References

Link	Tags
https://www.mozilla.org/security/advisories/mfsa2021-55/	vendor advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1732310	issue tracking permissions required vendor advisory

Frequently Asked Questions

What is the severity of CVE-2021-4126?: CVE-2021-4126 has been scored as a medium severity vulnerability.
How to fix CVE-2021-4126?: To fix CVE-2021-4126, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2021-4126 being actively exploited in the wild?: As for now, there are no information to confirm that CVE-2021-4126 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-4126?: CVE-2021-4126 affects Mozilla Thunderbird.

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