Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted device.
The vulnerability is due to improper handling of malformed packets. An unauthenticated, remote attacker could exploit this vulnerability by sending malicious network packets to the targeted device. If successful, the attacker could cause the device to become unresponsive, resulting in a DoS condition.
Cisco confirmed the vulnerability in a security advisory and released updated software.
Indicators of Compromise
Cisco has published a list of affected Cisco IOS Software releases in the security advisory. The Vendor Announcements section of this alert contains a link to the advisory.
The vulnerability is due to improper memory handling when processing Session Initiation Protocol (SIP) packets by Cisco IOS Software.
An unauthenticated, remote attacker could exploit the vulnerability by sending malicious SIP network messages to the targeted device. The processing of the malicious SIP messages could cause the device to use and fail to free memory, causing a memory leak error. The memory leak could cause the device to consume all available memory, rendering the device unavailable and resulting in a DoS condition.
To exploit the vulnerability, an attacker must send malicious SIP network messages to a targeted device. Depending on network configuration, devices that are handling SIP network traffic may be located on separate physical or logical networks, increasing the difficulty of an 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 may consider using IP-based access control lists (ACLs) to allow only trusted systems to access the affected systems.
Administrators are advised to monitor affected systems.
The Cisco Applied Intelligence team has created the following companion document to guide administrators in identifying and mitigating attempts to exploit this vulnerability prior to applying updated software: cisco-amb-20110928-voice
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.