Cisco Firewall Services Module (FWSM) and Cisco ASA 5500 Series Adaptive Security Appliance (ASA) contain multiple vulnerabilities that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.
These vulnerabilities are due to insufficient validation of user-supplied input processed by the affected software. An unauthenticated, remote attacker could exploit these vulnerabilities by sending crafted Distributed Computing Environment/Remote Procedure Call (DCERPC) packets to a vulnerable system. Processing these packets could cause a targeted device to reload, resulting in a DoS condition on the system.
Cisco has confirmed these vulnerabilities and released updated software.
Indicators of Compromise
The following releases of Cisco FWSM are vulnerable while running on Cisco Catalyst 6500 Series Switches and Cisco 7600 Series Routers with the DCERPC inspection engine enabled:
Cisco FWSM Releases prior to 3.2(24)
Cisco FWSM Releases 4.0.17 and prior
Cisco FWSM Releases prior to 4.1(7)
The following releases of Cisco ASA Software are also affected by these vulnerabilities:
Cisco ASA Releases prior to 8.3(2.25)
Cisco ASA Releases prior to 8.4(2.4)
Cisco ASA Releases prior to 8.5(1.12)
The vulnerabilities are due to insufficient validation of user-supplied input processed by the affected software. The DCERPC inspection engine of an affected device fails to validate DCERPC packets in a valid DCERPC session. These vulnerabilities can be triggered by IP version 4 and IP version 6 traffic. In addition, these vulnerabilities also affect both routed and transparent firewall modes in both single-context and multicontext modes.
An unauthenticated, remote attacker could exploit these vulnerabilities by sending crafted DCERPC packets to a vulnerable system for inspection. Processing these packets could cause a device to reload or possibly overflow the stack, which may allow the attacker to execute arbitrary commands.
To exploit these vulnerabilities, an attacker would need access to an internal network to send crafted packets to a vulnerable device. In a typical network configuration, such devices are placed on trusted, internal networks. This access requirement could limit the possibility of a successful exploit.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators may consider disabling the DCERPC inspection engine if this option is not required.
Administrators are advised to implement an intrusion prevention system (IPS) or intrusion detection system (IDS) to help detect and prevent attacks that attempt to exploit these vulnerabilities.
Administrators are advised to monitor affected systems.
Cisco customers with active contracts can obtain updates through the Software Center at the following link: Cisco. Cisco customers without contracts can obtain upgrades by contacting the Cisco Technical Assistance Center at 1-800-553-2447 or 1-408-526-7209 or via e-mail at firstname.lastname@example.org.
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.