CVE-2017-6731 in IOS XR
Summary
by MITRE
A vulnerability in Multicast Source Discovery Protocol (MSDP) ingress packet processing for Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause the MSDP session to be unexpectedly reset, causing a short denial of service (DoS) condition. The MSDP session will restart within a few seconds. More Information: CSCvd94828. Known Affected Releases: 4.3.2.MCAST 6.0.2.BASE. Known Fixed Releases: 6.3.1.19i.MCAST 6.2.3.1i.MCAST 6.2.2.17i.MCAST 6.1.4.12i.MCAST.
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Analysis
by VulDB Data Team • 12/31/2020
The vulnerability identified as CVE-2017-6731 resides within the Multicast Source Discovery Protocol implementation of Cisco IOS XR Software, specifically affecting the ingress packet processing mechanisms that govern MSDP session management. This weakness manifests as a remote denial of service condition that can be exploited by unauthenticated attackers without requiring any privileged access or credentials to execute the attack. The flaw operates at the network protocol level where MSDP packets are received and processed by routers configured with multicast routing capabilities, making it particularly concerning for network infrastructure devices that serve as core routing components in enterprise and service provider environments.
The technical nature of this vulnerability stems from insufficient validation and handling of malformed or specially crafted MSDP packets during the ingress processing phase. When an attacker sends maliciously constructed MSDP packets to a vulnerable Cisco IOS XR device, the system fails to properly process these packets and instead triggers an unexpected reset of the MSDP session. This reset causes temporary disruption to multicast routing information exchange between different multicast domains, effectively breaking the multicast forwarding path until the session automatically restarts within a few seconds. The vulnerability affects multiple release versions of Cisco IOS XR software, specifically those in the 4.3.2.MCAST, 6.0.2.BASE, and various other affected releases, while newer versions including 6.3.1.19i.MCAST, 6.2.3.1i.MCAST, 6.2.2.17i.MCAST, and 6.1.4.12i.MCAST have been patched to address the issue.
The operational impact of this vulnerability extends beyond simple service disruption as it can compromise the reliability of multicast services that many organizations depend upon for video streaming, real-time data distribution, and other time-sensitive applications. Network administrators may experience unexpected service interruptions that could affect critical business operations, particularly in environments where multicast routing is extensively used for content distribution or network monitoring. The automatic restart of MSDP sessions provides some resilience, but the frequency and timing of such disruptions can create cascading effects throughout the network infrastructure, potentially leading to more widespread connectivity issues.
Security professionals should implement immediate mitigation strategies including applying the relevant software patches provided by Cisco to address the vulnerability in affected systems. Network segmentation and access control measures can help reduce the attack surface by limiting direct access to multicast routing protocols from untrusted networks. Monitoring solutions should be enhanced to detect unusual MSDP session reset patterns that could indicate exploitation attempts. Organizations should also consider implementing network access control lists or firewall rules that restrict MSDP packet transmission to only trusted sources. This vulnerability aligns with CWE-20, which describes improper input validation, and maps to ATT&CK technique T1499.002 for network denial of service attacks, highlighting the need for comprehensive network security monitoring and incident response procedures to detect and respond to such threats effectively.