A flaw during verification of certain S/MIME signatures causes emails to be shown in Thunderbird as having a valid digital signature, even if the shown message contents aren't covered by the signature. The flaw allows an attacker to reuse a valid S/MIME signature to craft an email message with arbitrary content.
Created thunderbird tracking bugs for this issue:
Affects: fedora-all [bug 1677614]
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):