Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to errors in processing malformed Session Initiation Protocol (SIP) messages. 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 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 errors in processing malformed SIP messages. Affected devices accept SIP messages via TCP and UDP ports 5060 or TCP port 5061. An unauthenticated, remote attacker could exploit this vulnerability by sending a malicious SIP message to the targeted device. When processed, the message could cause the device to stop responding and reload, resulting in a DoS condition.
To exploit the vulnerability, an attacker must be able to send a malicious SIP message to a device. Systems that serve voice traffic may be located on separate physical or logical networks, making exploitation more difficult. An exploit could allow the attacker to cause the targeted device to fail and reload, potentially interrupting network services.
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 may consider disabling SIP listening ports on devices that are not required to process voice network traffic.
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 email@example.com.
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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.