Cisco ASA Adaptive Security Appliance (ASA) Software and Cisco ASA Services Module (ASASM) Software contain a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability exists because the affected software performs improper memory operations when handling crafted DHCP packets. An unauthenticated, remote attacker could exploit this vulnerability by sending malicious DHCP traffic to the affected device. Successful exploitation could allow the attacker to cause the targeted device to reload. Sustained attacks could result in a DoS condition.
Cisco has confirmed the vulnerability in a security advisory and released software updates.
Indicators of Compromise
Cisco ASA Software and Cisco ASASM Software Releases prior to the following are vulnerable:
The vulnerability is due to improper memory operations during the DHCP request packet process. When the affected software attempts to allocate memory for an internal DHCP data structure, a memory error condition could cause the targeted device to reload.
An unauthenticated, remote attacker could exploit this vulnerability by sending crafted DCHP packets to the affected device. When the affected software processes the malicious DHCP traffic, a memory error condition could allow the attacker to cause the targeted device to reload. Sustained attacks could result in a DoS condition.
To exploit the vulnerability, the attacker must send malicious requests to the targeted system, which would likely require the attacker to have access to trusted internal networks. This access requirement limits the likelihood 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.
By default, DHCP server is enabled on the inside interface of the Cisco ASA 5505 and on the management interface of all other Cisco ASA 5500 Series Adaptive Security Appliances. DHCP server is disabled by default on Cisco Catalyst 6500 Series ASA Services Module.
DHCP relay feature is not enabled by default on any Cisco ASA 5500 Series Adaptive Security Appliances and Cisco Catalyst 6500 Series ASA Services Module platforms.
DHCP relay and DHCP server features will trigger the DHCP request packet process.
Administrators are advised to apply the appropriate updates.
Administrators are advised to allow only trusted users to have network access.
Administrators may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
Administrators are advised to monitor critical 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.