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 on a targeted device.
The vulnerability is due to improper handling of crafted DHCPv6 packets by the affected software. An unauthenticated, remote attacker could exploit this vulnerability by sending a crafted request to a device that has the DHCPv6 server feature enabled. A successful exploit could allow the attacker to cause the targeted device to reload, denying service to legitimate users. Sustained attacks could result in a DoS condition.
Cisco has confirmed this vulnerability and released software updates.
Indicators of Compromise
Cisco has published a list of affected Cisco IOS Software and Cisco IOS XE Software releases in the security advisory. The Vendor Announcements section of this alert contains a link to the advisory.
The vulnerability is due to improper handling of crafted DHCPv6 packets destined for the DHCP server by the affected software. The vulnerability is triggered when the affected Cisco IOS device attempts to process a malformed DHCPv6 packet. Transit DHCPv6 packets, that the Cisco IOS device forwards, will not trigger this vulnerability.
An unauthenticated, remote attacker could exploit this vulnerability by sending a crafted DHCPv6 request to a targeted device that has the DHCPv6 server feature enabled. When the affected device processes the malicious request, an error condition may occur that the attacker could use to cause the targeted device to reload, denying service to legitimate users. Sustained attacks could result in a DoS condition.
Cisco IOS devices that are configured as a DHCP server for IPv4 are not affected by this vulnerability. In addition, Cisco devices that are configured as DHCPv6 clients or relay agents are not affected by this vulnerability.
Cisco indicates through the CVSS score that functional exploit code exists; however, the code is not known to be publicly available.
To exploit this vulnerability, the attacker may need access to trusted, internal network resources. In addition, the DHCPv6 server feature is not enabled by default. These access and configuration requirements reduce the likelihood of a successful exploit.
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.
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM
THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE ALERTS AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the distribution URL is an uncontrolled copy and may lack important information or contain factual errors. The information in this document is intended for end users of Cisco products
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.