Outlook Web Access (OWA) suffers from a vulnerability that allows direct access to files blocked by policy

This trick is mostly useful but can also be used for wrong purposes. Since it is so simple, it’s probably already known for some people.

If someone sends you a file through OWA but the file is blocked by a policy, this is what you can do:

1-Install firefox
2-Access your email and attachment with the following rule:

http://<hostname>/<OWA directory>/<mail box username>/Inbox/<email subject>.EML/<attachment filename>

E.g.:
http://webmail.example.com/Exchange/myusername/Inbox/virus.EML/virus.zip

The best way is to try in following order:

1- http://<hostname>/<OWA directory>/<mail box username>/Inbox – you see all your emails
2- http://<hostname>/<OWA directory>/<mail box username>/Inbox/<email subject>.EML – you see only your email with the blocked files
3- http://<hostname>/<OWA directory>/<mail box username>/Inbox/<email subject>.EML/<attachment filename> – you download the file

The actual address could be different for a couple of reasons. Try to check the attachment URL and use it like shown above.

This can also be exploited through a malicious email with a link inside pointing to the malware directly.

Server environment: Exchange/ OWA 2003 6.5.76*
Client environment: firefox 3.0.15

Ricardo Martins
CISA, ISO 27001/20000 LA
Compliance & Consulting Manager
 
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