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Credit:
The information has been provided by iDefense.
The original article can be found at:
http://labs.idefense.com/intelligence/vulnerabilities/display.php?id=475
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Vulnerable Systems:
* Clam AntiVirus ClamAV v0.90RC1.1.
* All versions prior to the 0.90 stable release are suspected to be vulnerable.
The vulnerability specifically exists due to a file descriptor leak. When clam encounters a cabinet header with a record length of zero it will return from a function without closing a local file descriptor. This can be triggered multiple times, eventually using up all but three of its available file descriptors. This prevents clam from scanning most archives, including zip and tar files.
Exploitation allows attackers to degrade the functionality of the ClamAV virus scanning service. Exploitation requires that attackers send a specially constructed CAB file through an e-mail gateway or personal anti-virus client using the ClamAV scanning engine.
When ClamAV is unable to scan an archive successfully because it has run out of descriptors, it will return an error status. Several mail servers that use clam were tested to see how they handled this status. Exim, as of version 4.50, features an option to build clamd support into it. It will reject a mail if clamd fails to scan it properly. Amavisd will also deny a mail that clamd cannot properly scan. This vulnerability can be used to deny service to users trying to send legitimate archives through the mail gateway.
CVE Information:
CVE-2007-0897
Disclosure Timeline:
* 02/07/2007 - Initial vendor notification
* 02/13/2007 - Initial vendor response
* 02/15/2007 - Coordinated public disclosure
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