CVE-2017-12319 in IOS XE
Summary
by MITRE
A vulnerability in the Border Gateway Protocol (BGP) over an Ethernet Virtual Private Network (EVPN) for Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the device to reload, resulting in a denial of service (DoS) condition, or potentially corrupt the BGP routing table, which could result in network instability. The vulnerability exists due to changes in the implementation of the BGP MPLS-Based Ethernet VPN RFC (RFC 7432) draft between IOS XE software releases. When the BGP Inclusive Multicast Ethernet Tag Route or BGP EVPN MAC/IP Advertisement Route update packet is received, it could be possible that the IP address length field is miscalculated. An attacker could exploit this vulnerability by sending a crafted BGP packet to an affected device after the BGP session was established. An exploit could allow the attacker to cause the affected device to reload or corrupt the BGP routing table; either outcome would result in a DoS. The vulnerability may be triggered when the router receives a crafted BGP message from a peer on an existing BGP session. This vulnerability affects all releases of Cisco IOS XE Software prior to software release 16.3 that support BGP EVPN configurations. If the device is not configured for EVPN, it is not vulnerable. Cisco Bug IDs: CSCui67191, CSCvg52875.
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Analysis
by VulDB Data Team • 09/09/2024
The vulnerability identified as CVE-2017-12319 represents a critical flaw in Cisco IOS XE Software's implementation of Border Gateway Protocol over Ethernet Virtual Private Network (BGP-EVPN) functionality. This weakness specifically targets the handling of BGP update packets within the MPLS-Based Ethernet VPN framework as defined in RFC 7432, creating a potential vector for remote code execution and system instability. The vulnerability stems from improper calculation of IP address length fields within specific BGP route update messages, particularly when processing Inclusive Multicast Ethernet Tag Routes or MAC/IP Advertisement Routes. The flaw exists in the transitional implementation between different software releases, making devices running IOS XE versions prior to 16.3 susceptible to exploitation.
The technical exploitation of this vulnerability occurs through the manipulation of BGP packet structures during an established session, where an unauthenticated remote attacker can craft malicious update messages that trigger memory corruption or system instability. When the affected device receives these crafted packets, the miscalculated IP address length field causes the router's BGP processing module to behave unpredictably, potentially leading to complete system reloads or corruption of the BGP routing table. This behavior aligns with CWE-125, which describes out-of-bounds read vulnerabilities, and CWE-248, addressing unchecked exceptions in software implementations. The attack vector operates at the network layer, leveraging the BGP protocol's trust-based architecture where legitimate peers are expected to send valid routing updates.
The operational impact of this vulnerability extends beyond simple denial of service, as the corruption of BGP routing tables can create cascading network failures across interconnected systems. Network instability resulting from this vulnerability can affect large-scale deployments where BGP-EVPN is actively utilized for multi-tenant network segmentation and service delivery. The DoS condition manifests through either complete device reloads that require manual intervention or routing table corruption that can cause traffic blackholing, path flapping, or incorrect route propagation throughout the network infrastructure. This vulnerability particularly affects service providers and enterprises that rely on EVPN for Layer 2VPN services, as the disruption can impact multiple customer connections simultaneously.
Mitigation strategies for CVE-2017-12319 should prioritize immediate software upgrades to IOS XE release 16.3 or later, which contain the necessary patches to correct the IP address length calculation logic. Network administrators should implement BGP route filtering and peer authentication mechanisms to limit exposure, while also monitoring for suspicious BGP update patterns that might indicate exploitation attempts. The implementation of BGP monitoring tools and anomaly detection systems can help identify malformed packets before they cause system instability. From an ATT&CK framework perspective, this vulnerability maps to T1071.004 (Application Layer Protocol: DNS) and T1499.004 (Endpoint Denial of Service: Resource Exhaustion) where the attack leverages protocol implementation flaws to exhaust system resources or cause service disruption. Organizations should also consider implementing network segmentation and access control lists to limit BGP peer relationships to trusted networks only, reducing the attack surface for remote exploitation attempts.