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Vulnerability of Cisco PIX: denial of service of DHCP relay

Synthesis of the vulnerability 

An attacker can generate a memory leak when several DHCP servers are configured.
Impacted software: ASA.
Severity of this computer vulnerability: 2/4.
Creation date: 03/05/2007.
Références of this announce: 91337, BID-23763, CERTA-2007-AVI-198, cisco-sr-20070502-pix, CSCsh50277, CVE-2007-2461, VIGILANCE-VUL-6784, VU#530057.

Description of the vulnerability 

The DHCP relay of firewall transmits exchanges of DHCP protocol between client and server:
 - DHCPDISCOVER, DHCPOFFER, DHCPREQUEST and DHCPACK
 - DHCPINFORM and DHCPACK

When relay communicates with several DHCP servers, several exchanges occurs in parallel. However, in this case, a memory area storing an Ethernet frame containing DHCPACK is not freed.

An attacker can therefore send numerous DHCP packets in order to exhaust memory by steps of 1550 bytes.
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This computer vulnerability impacts software or systems such as ASA.

Our Vigil@nce team determined that the severity of this weakness bulletin is medium.

The trust level is of type confirmed by the editor, with an origin of LAN.

An attacker with a expert ability can exploit this weakness.

Solutions for this threat 

Cisco PIX: version 7.2.2.15.
Version 7.2.2.15 is corrected:
  http://www.cisco.com/pcgi-bin/tablebuild.pl/pix-interim
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