CVE-2015-4223 in IOS XR
Summary
by MITRE
Cisco IOS XR 5.1.3 allows remote attackers to cause a denial of service (process reload) via crafted MPLS Label Distribution Protocol (LDP) packets, aka Bug ID CSCuu77478.
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Analysis
by VulDB Data Team • 05/21/2022
Cisco IOS XR 5.1.3 contains a critical vulnerability in its MPLS Label Distribution Protocol implementation that enables remote attackers to trigger a denial of service condition through carefully crafted LDP packets. This vulnerability represents a significant security flaw in the network infrastructure software that powers critical routing and switching operations across enterprise and service provider networks. The issue manifests when the system processes malformed or specially constructed LDP messages that cause the affected process to reload unexpectedly, resulting in temporary service interruption and potential network instability.
The technical root cause of this vulnerability lies in insufficient input validation within the MPLS LDP processing module of the IOS XR operating system. When the system receives crafted LDP packets containing malformed label information or improper protocol structures, the parsing routine fails to properly handle these edge cases, leading to an uncontrolled process restart. This behavior falls under CWE-129, Input Validation, and CWE-248, Uncaught Exception, as the system does not adequately sanitize incoming LDP messages before processing them. The vulnerability specifically affects the Label Distribution Protocol implementation which is fundamental to MPLS network operations, making it particularly dangerous in environments where MPLS services are heavily utilized.
The operational impact of this vulnerability extends beyond simple service disruption as it can affect critical network infrastructure components that rely on MPLS for traffic engineering and service delivery. Network administrators may experience unexpected service outages, particularly in environments where LDP is actively used for label distribution between routers. The process reload triggered by these malicious packets can cause temporary loss of routing information and potentially disrupt end-to-end connectivity for MPLS-based services. This vulnerability is especially concerning in service provider networks where continuous availability is paramount and where the failure of core routing processes can cascade across multiple network segments.
Organizations affected by this vulnerability should immediately implement mitigations including network segmentation to isolate MPLS LDP traffic, deploying access control lists to filter suspicious LDP packets, and applying the appropriate Cisco security patches. The recommended remediation involves upgrading to Cisco IOS XR software versions that contain the fix for CSCuu77478, which typically includes enhanced input validation and proper exception handling for LDP message processing. Network security teams should also consider implementing monitoring solutions to detect anomalous LDP traffic patterns that could indicate exploitation attempts, aligning with ATT&CK technique T1071.004 for Application Layer Protocol: DNS to detect potential reconnaissance activities. Additionally, implementing rate limiting on LDP sessions and disabling unnecessary LDP functionality on network perimeters can significantly reduce the attack surface and mitigate the risk of successful exploitation.