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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-126135

SMTP and POP3 response injection when using STARTTLS

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Status
Published
Published
Updated
Assigning organization
mozilla

Description

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.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Mozilla Thunderbird

  • 153.7 to ≤ 153.*unaffected
  • 160 to ≤ *unaffected

References