What’s Vulnerable › Vulnerabilities

CVE-2021-29969

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-08-05 · updated 2026-06-17
• Weakness: CWE-552

Description

If Thunderbird was configured to use STARTTLS for an IMAP connection, and an attacker injected IMAP server responses prior to the completion of the STARTTLS handshake, then Thunderbird didn't ignore the injected data. This could have resulted in Thunderbird showing incorrect information, for example the attacker could have tricked Thunderbird to show folders that didn't exist on the IMAP server. This vulnerability affects Thunderbird < 78.12.

Affected products

• Mozilla Thunderbird: before 78.12 — fixed in 78.12

How to fix

Upgrade to a fixed version: Mozilla Thunderbird 78.12. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1682370
• https://security.gentoo.org/glsa/202208-14
• https://www.mozilla.org/security/advisories/mfsa2021-30/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1682370
• https://security.gentoo.org/glsa/202208-14
• https://www.mozilla.org/security/advisories/mfsa2021-30/

Get alerted when CVE-2021-29969 or the next vulnerability affects your stack