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 the improper processing of crafted Session Initiation Protocol (SIP) packets by the affected software when configured with the Zone-Based Firewall feature enabled to inspect SIP packets. An unauthenticated, remote attacker could exploit this vulnerability by sending crafted SIP messages through a vulnerable device. If successful, the attacker could cause the device to reload or trigger memory leaks that may result in system instabilities 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 the improper processing of crafted SIP packets by the affected software when configured with the Zone-Based Firewall feature enabled to inspect SIP packets. When crafted SIP packets are processed, the packets could cause the system to consume and fail to free memory resources, resulting in a memory leak that may cause system instabilities due to a lack of memory resources. The vulnerability is exploitable only through transit SIP packets traveling through the vulnerable device.
An unauthenticated, remote attacker could exploit this vulnerability by sending specially crafted SIP messages via TCP/UDP port 5060 or TCP port 5061 through a vulnerable device. If successful, the attacker could cause the device to reload or trigger memory leaks that may result in system instabilities, leading to a DoS condition. Repeated attacks could result in a sustained DoS condition on the affected device.
To exploit the vulnerability, an attacker must send malicious SIP packets to the affected system.† Depending on the configuration of perimeter filtering devices, exploitation may require access to internal networks because external connections using SIP may be restricted.
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 may consider configuring the Cisco IOS Software Zone-Based Firewall feature without the SIP inspection option as a mitigation for this vulnerability.
Administrators are advised to monitor affected 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.