Mutt: failure to check server certificate in SMTP TLS connection

2011.03.18
Credit: dave b
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-20


Ogólna skala CVSS: 5.8/10
Znaczenie: 4.9/10
Łatwość wykorzystania: 8.6/10
Wymagany dostęp: Zdalny
Złożoność ataku: Średnia
Autoryzacja: Nie wymagana
Wpływ na poufność: Częściowy
Wpływ na integralność: Częściowy
Wpływ na dostępność: Brak

Hi all. It seems that mutt fails to check the validity of a SMTP servers certificate during a TLS connection. In my mutt configuration I have set ssl_starttls = yes set ssl_force_tls = yes However, after performing the steps below I found that mutt did not properly validate the remote servers SMTP tls certificate. This means that an attacker could potentially MITM a mutt user connecting to their SMTP server even when the user has forced a TLS connection. Steps to test this: 1. I set in my hosts file the ip for smtp.gmail.com to be bound to mail.lolok.com in /etc/hosts 74.125.127.109 mail.LOLOK.com 2.Then I changed my set smtp_url = "smtp://MYUSERNAME () smtp gmail com:587/" to be set smtp_url = "smtp://MYUSERNAME () mail lolok com:587/" 3. I opened up mutt and emailed my self. I note that I saw mutt say "connecting to mail.lolok.com". I feel that this is an issue because mutt _does_ actually perform IMAP server certificate validation (at least it did when I last tested it :P).

Referencje:

http://seclists.org/fulldisclosure/2011/Mar/87
http://xforce.iss.net/xforce/xfdb/66015
http://www.securityfocus.com/bid/46803


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