Cisco IOS Software and Cisco IOS XE Software contain a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition.
The vulnerability is due to errors in the RSVP feature. An unauthenticated, remote attacker could exploit this vulnerability to cause the targeted device to stop responding, 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.
Only specific configurations on affected devices are vulnerable. A device is vulnerable if both the following conditions are met:
A VPN routing and forwarding (VRF) instance is configured without RSVP
At least one other interface (physical or virtual), not in the same VRF, is configured with RSVP
The vulnerability is due to errors in the RSVP feature when used on a device configured with VRF instances.
An unauthenticated, remote attacker with limited knowledge of the targeted infrastructure could exploit this vulnerability by submitting valid, crafted RSVP packets with set conditions to an affected device, resulting in a wedge of the receive queue of any RSVP ingress interface. The resulting interface wedge could lead to loss of connectivity, loss of routing protocol adjacency, or other DoS conditions.
To exploit this vulnerability, the attacker would need knowledge of the affected infrastructure and the ability to submit RSVP packets to the targeted system. To achieve this objective, the attacker may need access to trusted, internal network resources. This access requirement reduces the exposure of this vulnerability.
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 devices.
Administrators are advised to allow only trusted users to have network access.
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.