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 TCP segment reassembly 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 large TCP reassembled packets that are being processed by NAT and ALG features on the affected device. An attacker could exploit this vulnerability by sending a TCP packet that is large after the reassembly to traverse a vulnerable device. Only packets being handled by NAT and ALG features have a potential to cause an affected device to reload. An exploit could allow the attacker to cause a reload of the affected device, resulting in a DoS condition.
Cisco has confirmed the vulnerability in a security advisory and released software updates.
Cisco IOS XE Software versions prior to 3.7.3S and 3.8.1S are affected.
Only devices performing ALG and NAT inspection are vulnerable, which may reduce the number of vulnerable systems in many 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 handling of fragmented packets by the Cisco IOS XE Software network address translation (NAT) and application layer gateway (ALG) inspection features.
An unauthenticated, remote attacker could exploit this vulnerability by sending malicious fragmented TCP packets within communications that transit interfaces on a vulnerable device performing NAT and ALG inspection. The reassembly of the malicious fragmented packets could cause the device to reload, resulting in a DoS condition.
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
3.7S Base, .0, .1, .2 | 3.8S Base, .0, .1
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