Cisco Advisory - The Cisco Secure PIX firewall feature "mailguard," which limits SMTP commands to a specified minimum set of commands, can be bypassed. This vulnerability can be exploited to bypass SMTP command filtering. All users of Cisco Secure PIX Firewalls with software versions up to and including 4.4(5), 5.0(3), 5.1(2) and 5.2(1) that provide access to SMTP Mail services are at risk. The IOS Firewall featureset is not affected by either of the above defects.
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