CVE-2017-6599 in IOS XR
Summary
by MITRE
A vulnerability in Google-defined remote procedure call (gRPC) handling in Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause the Event Management Service daemon (emsd) to crash due to a system memory leak, resulting in a denial of service (DoS) condition. This vulnerability affects Cisco IOS XR Software with gRPC enabled. More Information: CSCvb14433. Known Affected Releases: 6.1.1.BASE 6.2.1.BASE. Known Fixed Releases: 6.2.1.22i.MGBL 6.1.22.9i.MGBL 6.1.21.12i.MGBL 6.1.2.13i.MGBL.
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Analysis
by VulDB Data Team • 11/27/2022
The vulnerability described in CVE-2017-6599 represents a critical denial of service weakness within Cisco IOS XR Software that leverages the gRPC remote procedure call framework. This issue specifically targets the Event Management Service daemon (emsd) which is responsible for handling system events and monitoring operations within the network infrastructure. The flaw manifests when gRPC functionality is enabled on affected Cisco IOS XR devices, creating an exploitable condition that can be triggered remotely without authentication requirements. The vulnerability stems from improper memory management within the emsd process, where repeated gRPC requests can cause progressive memory consumption that eventually leads to system instability and complete service disruption. This represents a classic memory leak scenario that can be amplified through repeated exploitation attempts, making it particularly dangerous in production network environments where continuous availability is essential.
The technical implementation of this vulnerability involves the manipulation of gRPC communication protocols to trigger memory allocation patterns that are not properly cleaned up during normal operation. When an attacker sends specifically crafted gRPC requests to a vulnerable Cisco IOS XR device, the emsd daemon processes these requests and allocates memory resources without subsequent deallocation, creating a progressive memory consumption pattern. This memory leak eventually exhausts available system resources, forcing the emsd daemon to terminate unexpectedly and causing the Event Management Service to become unavailable. The vulnerability is particularly concerning because it operates at the system level within the IOS XR operating system, affecting core infrastructure services rather than application-level components. This aligns with CWE-401: Improper Release of Memory Before Removing Last Reference, which specifically addresses memory management flaws that result in resource exhaustion.
The operational impact of CVE-2017-6599 extends beyond simple service disruption to potentially compromise network infrastructure reliability and availability. Network operators relying on Cisco IOS XR devices for critical infrastructure services face significant risk when this vulnerability is present, as the denial of service condition affects the Event Management Service daemon which is integral to system monitoring and event handling capabilities. The vulnerability can be exploited remotely, meaning attackers do not require physical access or network credentials to trigger the condition, making it particularly dangerous in exposed network environments. The affected releases indicate that this vulnerability spans multiple versions of the IOS XR software, suggesting it was present for an extended period and likely exploited in the wild. The fact that multiple fixed releases are available demonstrates that Cisco recognized the severity of the issue and provided patches across different software version lines to address the memory management flaw.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems to the recommended fixed releases, which include versions 6.2.1.22i.MGBL, 6.1.22.9i.MGBL, 6.1.21.12i.MGBL, and 6.1.2.13i.MGBL. Network administrators should implement network segmentation and access controls to limit exposure of vulnerable devices to untrusted networks, while also monitoring for unusual patterns in system resource consumption that might indicate exploitation attempts. Additionally, implementing intrusion detection systems capable of identifying abnormal gRPC traffic patterns and establishing baseline memory usage monitoring for emsd processes can provide early warning capabilities. The vulnerability's classification under ATT&CK technique T1499.004 (Endpoint Denial of Service) highlights its potential for being used as part of broader attack campaigns targeting network infrastructure availability. Organizations should also consider implementing configuration management practices to disable gRPC functionality on devices where it is not required, reducing the attack surface for this specific vulnerability.