Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability exists due to errors in processing Skinny Client Control Protocol (SCCP) packets. An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious request to the targeted device. Successful exploitation could allow the attacker to cause the device to reload, resulting in a DoS condition.
Cisco has 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 errors in processing SCCP packets. The Unified Call Manager Express feature of Cisco IOS Software uses SCCP to support IP phones. By default, devices accept SCCP packets on TCP port 2000, although the port is configurable. Devices accept SCCP requests only from registered IP addresses; however, the autoregistration feature is enabled by default and could allow an attacker to register an IP address prior to an exploit.
An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious packet to the targeted device. When processed, the packet could cause an error condition that causes the device to reload, resulting in a DoS condition.
To exploit this vulnerability, an attacker may require access to internal networks. The attacker must send requests to a targeted device from a registered IP address. If the autoregistration feature is enabled, as it is by default, the attacker could register an IP address prior to exploitation.
If an exploit is successful, the attacker could cause the system to reload. A stream of malicious packets could cause the device to reload as long as the stream continues.
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 available software 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 implement an intrusion prevention system (IPS) or intrusion detection system (IDS) to help detect and prevent attacks that attempt to exploit this vulnerability.
Administrators are advised to monitor critical 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-20100324-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.