It was found that Pidgin's SSL/TLS plug-ins had a flaw in the certificate validation functionality. An attacker could use this flaw to create a fake certificate, that Pidgin would trust, which could be used to conduct man-in-the-middle attacks against Pidgin.
DescriptionMurray McAllister
2014-10-21 03:16:13 UTC
It was reported that the SSL/TLS plug-ins failed to check that the Basic Constraints extension allowed intermediate certificates to act as Certificate Authorities (CAs). An attacker could use this flaw to create a fake certificate that Pidgin would trust, which could be used for man-in-the-middle attacks.
This is the same situation as described in http://www.thoughtcrime.org/ie-ssl-chain.txt
Acknowledgments:
Name: the Pidgin project
Upstream: Jacob Appelbaum, Moxie Marlinspike
Comment 1Murray McAllister
2014-10-21 03:17:13 UTC
Analysis
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Basic Constraints checking is missing for the certificates in the code for pidgin, so attacker who already has an valid CA-Signed Certificate of any domain can generate a valid CA-Signed certificate and request signature for any other domain. As there are no checks for Basic Constraints it fails to the check if there is an man-in-the-middle attack executed with the help of malicious certificate whenever there is SSL connection intiated with the server.