Cisco has disclosed a denial-of-service (DoS) vulnerability in the Border Gateway Protocol (BGP) confederation implementation within Cisco IOS XR Software. This vulnerability could allow an unauthenticated, remote attacker to disrupt network operations by causing a DoS condition.
Vulnerability Details
This issue arises due to memory corruption when a BGP update is created with an AS_CONFED_SEQUENCE attribute containing 255 autonomous system (AS) numbers. An attacker could exploit this vulnerability by sending a crafted BGP update message or if the network is designed in such a way that the AS_CONFED_SEQUENCE attribute reaches 255 AS numbers or more.
A successful exploit may lead to memory corruption, forcing the BGP process to restart, ultimately resulting in a DoS condition. To exploit this vulnerability, an attacker must control a BGP confederation speaker within the same autonomous system as the target or operate in a network environment where the AS_CONFED_SEQUENCE attribute grows to 255 AS numbers or more.
Affected Products
At the time of disclosure, this vulnerability affects Cisco IOS XR Software when BGP confederation is enabled.
Workarounds
A temporary workaround exists to mitigate this vulnerability. Since the issue occurs when the AS_CONFED_SEQUENCE attribute reaches 255 AS numbers, restricting it to 254 or fewer AS numbers can help prevent exploitation.
This can be achieved by implementing a routing policy that drops BGP updates with excessively long AS path lengths on confederation peers.
Much as this workaround has been tested successfully in a controlled environment, organizations should evaluate its applicability within their own networks to ensure minimal disruption. Any mitigation steps should be carefully assessed for potential impacts on network performance and functionality.
Fixed Software
Cisco has released software updates to address this vulnerability. Organizations are encouraged to check Cisco’s Security Advisories page regularly to ensure they are using the latest and most secure software versions.
Before performing software upgrades, customers should verify that their devices have sufficient memory and that their current hardware and software configurations remain compatible with the new release. If any uncertainties arise, contacting Cisco Technical Assistance Center (TAC) or a contracted maintenance provider is recommended.
For more details, https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-bgp-dos-O7stePhX