CVE-2026-126135
What it is
If an attacker was able to perform a man-in-the-middle attack on an SMTP or POP3 server connection using STARTTLS, the attacker could inject server responses before the TLS handshake completed. Thunderbird would process these responses after the handshake, as if they had been received from the server over the encrypted connection. This could be used to make Thunderbird report a different outcome for sending or fetching mail, and to show attacker-controlled text in error messages. The encrypted connection itself was not compromised, and credentials were not exposed. Connections using SSL/TLS instead of STARTTLS were not affected. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.
At a glance
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: not scored yet.
- Severity: not scored yet.
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Record status
- Awaiting Analysis
Is it in your code?
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Read https://cve-list.com/agent/cve/CVE-2026-126135.md and follow it. Check whether this project is affected by CVE-2026-126135. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
