Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service condition. Updates are available.
A vulnerability in the Zone-Based Firewall (ZBFW) TCP or UDP inspection feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition.
The vulnerability is due to improper processing of malformed ICMP error packets traversing a vulnerable device that belong to a TCP or UDP connection that is inspected by a ZBFW. An attacker could exploit this vulnerability by sending a number of malformed ICMP error packets that belong to an inspected TCP or UDP session. An exploit could allow the attacker to cause a reload of the affected device, resulting in DoS condition.
Cisco has confirmed the vulnerability in a security advisory and released software updates.
Cisco IOS XE Software versions prior to 3.4.2S and 3.5.1S are affected.
Some environments may block ICMP packets from untrusted networks, possibly requiring an attacker have access to internal networks prior to conducting an exploit. The threat of exploitation is lower in such environments.
An unauthenticated, remote attacker could exploit this vulnerability to cause a vulnerable device to reload, resulting in a DoS condition.
The vulnerability is due to improper processing of ICMP packets by the Cisco IOS XE Software ZBFW inspection feature.
An unauthenticated, remote attacker could exploit the vulnerability by sending malicious ICMP packets to a vulnerable device or by sending packets that would transit interfaces on the device. The processing of the malicious packets could cause an error condition, resulting in the device restarting.
Administrators are advised to apply the appropriate updates.
Administrators can help protect affected systems from external attacks by using a solid firewall strategy.
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 email at firstname.lastname@example.org.
The security vulnerability applies to the following combinations of products.
Cisco IOS XE Software
3.4S .0, .1 | 3.5S Base, .0
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