CVE-2017-3856 in IOX XE
Summary
by MITRE
A vulnerability in the web user interface of Cisco IOS XE 3.1 through 3.17 could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to insufficient resource handling by the affected software when the web user interface is under a high load. An attacker could exploit this vulnerability by sending a high number of requests to the web user interface of the affected software. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. To exploit this vulnerability, the attacker must have access to the management interface of the affected software, which is typically connected to a restricted management network. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS XE Software, if the web user interface of the software is enabled. By default, the web user interface is not enabled. Cisco Bug IDs: CSCup70353.
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Analysis
by VulDB Data Team • 08/28/2024
The vulnerability described in CVE-2017-3856 represents a critical denial of service weakness within Cisco IOS XE software versions 3.1 through 3.17, specifically affecting the web user interface component. This flaw stems from inadequate resource management when the web interface experiences elevated request loads, creating a scenario where malicious actors can trigger system instability through carefully crafted network traffic patterns. The vulnerability operates at the application layer of the network stack, targeting the software's ability to process concurrent connections and requests without proper resource allocation controls.
The technical exploitation mechanism relies on sending an excessive volume of requests to the web user interface, which causes the system to consume resources beyond normal operational parameters. This resource exhaustion leads to system instability and ultimately results in device reboot cycles, effectively creating a denial of service condition that disrupts legitimate network operations. The attack vector requires network access to the management interface, typically restricted to administrative networks, though this limitation does not prevent exploitation in environments where such access has been compromised. The vulnerability demonstrates poor input validation and resource handling practices that align with CWE-400 weakness categories related to resource exhaustion attacks.
From an operational perspective, this vulnerability presents significant risk to network availability and service continuity, particularly in enterprise environments where network device stability is paramount. The DoS condition created by the vulnerability can result in extended downtime, requiring manual intervention to restore system functionality and potentially impacting critical network services. Organizations utilizing affected Cisco IOS XE versions face potential disruption to their network management capabilities, as the web interface becomes unavailable during exploitation events. The default disablement of the web interface provides some protection, but many organizations enable this feature for administrative convenience, creating exposure windows that attackers can exploit.
Security practitioners should implement multiple layers of defense to mitigate this vulnerability, beginning with immediate software upgrades to patched IOS XE versions that address the resource handling deficiencies. Network segmentation and access control measures should be enforced to limit management interface access to authorized administrative networks only, reducing the attack surface for potential exploitation. Monitoring systems should be configured to detect unusual request patterns and high load conditions that may indicate attempted exploitation, providing early warning capabilities. The vulnerability's characteristics align with ATT&CK technique T1499.004 related to network denial of service attacks, emphasizing the need for robust network resilience and monitoring capabilities. Organizations should also consider disabling the web interface entirely when not required for administrative tasks, as this represents the most effective mitigation approach against this specific vulnerability class.