Cisco Carrier Routing System contains a vulnerability that could allow an unauthenticated, remote attacker to bypass security protections and gain unauthorized access. Updates are available.
Cisco Carrier Routing System contains a vulnerability that could allow an unauthenticated, remote attacker to bypass security protections and gain unauthorized network access.
The vulnerability is due to improper handling of IP version 4 (IPv4) fragments in the affected device. An unauthenticated, remote attacker could exploit this vulnerability by sending malicious requests to the device. When processed, the requests could bypass access control entries (ACEs), allowing the attacker to send network requests to restricted network segments.
Cisco has confirmed this vulnerability and released software updates.
Cisco Carrier Routing System with software version 3.9, 4.0, or 4.1 is vulnerable.
The vulnerability affects only systems that use ACLs to restrict access to specific network segments or hosts and only for noninitial IPv4 fragments. This vulnerability does not apply to nonfragments or to the initial fragment.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
An unauthenticated, remote attacker could exploit the vulnerability to bypass ACEs and gain unauthorized network access.
The vulnerability occurs because the IPv4 protocol is ignored when matching noninitial fragments to an ACE. This vulnerability applies only when noninitial IPv4 fragments with any protocol match the ACE. Noninitial fragments are those with a fragment offset not equal to zero.
An unauthenticated, remote attacker could exploit this vulnerability by sending malicious requests to the system. The device may allow the attacker to bypass an ACE by using fragmented packets to gain unauthorized network access.
Administrators are advised to apply the appropriate updates.
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 email@example.com.
The security vulnerability applies to the following combinations of products.
Cisco Carrier Routing System (CRS)
3.9Base | 4.0Base | 4.1Base
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