Cisco IOS Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on a targeted system.
The vulnerability is due to improper processing of Session Initiation Protocol (SIP) packets in transit while NAT is performed on a targeted device. An unauthenticated, remote attacker could exploit this vulnerability by sending crafted SIP packets via UDP port 5060 to a device that is performing NAT for SIP packets. A successful exploit could allow an attacker to cause the device to reload, resulting in a DoS condition.
Cisco confirmed this vulnerability and software updates are available.
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 processing of SIP packets in transit while performing NAT. The NAT SIP application layer gateway (ALG) feature must be enabled to trigger this vulnerability.
An unauthenticated, remote attacker could exploit this vulnerability by sending crafted SIP packets via UDP port 5060 to a targeted device that is performing NAT for SIP packets. When processed, the packets could cause the device to reload, resulting in a DoS condition.
The NAT SIP ALG is enabled by default in Cisco IOS images that include the NAT SIP ALG feature. Administrators are advised to disable this feature as described in the Safeguards section of this alert if the feature is not needed.
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 software updates.
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 may consider disabling the NAT SIP ALG feature if this option is not needed by issuing the no ip nat service sip udp port 5060 global configuration command.
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.