Memory Safety Violation via Malformed Mail Header in Thunderbird <140.16
CVE-2026-92238 Published on September 15, 2026
Ambiguous parsing of mail headers
A maliciously constructed mail header could lead to multiple fields being parsed as one, or potential memory safety violations. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.
Vulnerability Analysis
CVE-2026-92238 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.
Weakness Type
What is a HTTP Request Smuggling Vulnerability?
When malformed or abnormal HTTP requests are interpreted by one or more entities in the data flow between the user and the web server, such as a proxy or firewall, they can be interpreted inconsistently, allowing the attacker to "smuggle" a request to one device without the other device being aware of it.
CVE-2026-92238 has been classified to as a HTTP Request Smuggling vulnerability or weakness.
Products Associated with CVE-2026-92238
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Affected Versions
Mozilla Thunderbird:- Version 140.16, <= 140.* is unaffected.
- Version 153.3, <= 153.* is unaffected.
- Version 156, <= * is unaffected.