offlineimap STARTTLS stripping vulnerability fix analysis (RFC 2595 §9)

Vulnerability Overview This vulnerability involves a STARTTLS downgrade attack in the software. When the configuration is set to but the server does not support STARTTLS, the previous code would silently return without attempting TLS, leaving the connection in plaintext. RFC 2595 Section 9 explicitly describes this attack vector: a man-in-the-middle (MitM) attacker can remove STARTTLS from the capability list or generate a failure response, thereby forcing the use of a plaintext connection. Impact Scope Affected Versions: All unpatched versions of . Attack Scenario: A man-in-the-middle attacker can force the use of a plaintext connection by removing the STARTTLS capability or generating a failure response, thereby stealing sensitive information. Remediation Fix Measure: When is configured as but the server does not support STARTTLS, the program will issue a warning and attempt STARTTLS. If the server indeed does not support it, will throw an error. The existing error handling path will raise an and abort the connection. If successful, TLS will be established normally. Specific Behavior: - Server does not support STARTTLS (possible IMTP stripping): Do not attempt STARTTLS. - Log a warning to alert the user. - Attempt STARTTLS. - If the server rejects: Raise and abort the connection. - If the server accepts: Establish TLS and continue synchronization. Code Changes References Reporter: hartwork Reference Link: RFC 2595 §9 Summary This fix ensures that attempts to establish a TLS connection even if the server does not support STARTTLS, and aborts the connection upon failure, thereby preventing man-in-the-middle attacks.

Goal Reached Thanks to every supporter — we hit 100%!

offlineimap STARTTLS stripping vulnerability fix analysis (RFC 2595 §9)

More from this source