CVE-2016-9205 in IOS XR
Summary
by MITRE
A vulnerability in the HTTP 2.0 request handling code of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause the Event Management Service daemon (emsd) to crash, resulting in a denial of service (DoS) condition. More Information: CSCvb14425. Known Affected Releases: 6.1.1.BASE. Known Fixed Releases: 6.1.2.6i.MGBL 6.1.22.9i.MGBL 6.2.1.14i.MGBL.
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Analysis
by VulDB Data Team • 07/05/2019
The vulnerability identified as CVE-2016-9205 resides within the HTTP 2.0 request handling implementation of Cisco IOS XR Software, representing a critical security flaw that affects network infrastructure devices. This issue specifically targets the Event Management Service daemon known as emsd, which serves as a crucial component for managing system events and logging activities within the IOS XR operating system. The vulnerability stems from inadequate input validation and processing mechanisms within the HTTP 2.0 protocol handler, creating an exploitable condition that can be triggered remotely without authentication requirements. The flaw manifests when the system receives specially crafted HTTP 2.0 requests that cause the emsd daemon to terminate unexpectedly, leading to a complete denial of service condition that disrupts normal network operations.
The technical exploitation of this vulnerability occurs through malformed HTTP 2.0 requests that are processed by the affected IOS XR software versions. When the emsd daemon encounters these crafted requests, it fails to properly handle the malformed data structures or protocol violations, resulting in an uncontrolled crash of the service. This crash represents a classic buffer overflow or memory corruption scenario where the daemon's processing logic does not adequately validate or sanitize incoming HTTP 2.0 request parameters. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors that can lead to service disruption. The specific nature of the flaw indicates insufficient bounds checking in the HTTP 2.0 parser implementation, allowing attackers to manipulate the protocol state machine in a way that triggers the daemon termination.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise network availability and reliability for organizations relying on Cisco IOS XR devices. Network administrators may experience unexpected downtime of critical infrastructure services, potentially affecting routing operations, monitoring capabilities, and overall network performance. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter, making it particularly dangerous for publicly accessible devices. This vulnerability directly impacts the availability component of the CIA triad and can be classified under the MITRE ATT&CK framework's T1499.1 technique, which describes network denial of service attacks that target system availability. The DoS condition affects not just the specific service but can potentially cascade to other dependent network functions that rely on the Event Management Service for proper operation.
Organizations affected by this vulnerability should immediately implement the recommended remediation measures, including applying the vendor-provided software patches and updates. Cisco has released fixed versions in releases 6.1.2.6i.MGBL, 6.1.22.9i.MGBL, and 6.2.1.14i.MGBL, which contain the necessary code modifications to address the HTTP 2.0 request handling flaws. Network security teams should conduct comprehensive vulnerability assessments to identify all affected devices within their infrastructure and prioritize patch deployment accordingly. Additional mitigations may include implementing network segmentation to limit exposure, configuring access control lists to restrict HTTP 2.0 traffic, and monitoring for suspicious network activity that could indicate exploitation attempts. The vulnerability demonstrates the importance of proper protocol implementation validation and highlights the need for robust input sanitization in network service implementations. Organizations should also consider implementing intrusion detection systems that can identify and alert on anomalous HTTP 2.0 traffic patterns that may indicate exploitation attempts.