CVE-2017-15655 in AsusWRT
Summary
by MITRE
Multiple buffer overflow vulnerabilities exist in the HTTPd server in Asus asuswrt version <=3.0.0.4.376.X. All have been fixed in version 3.0.0.4.378, but this vulnerability was not previously disclosed. Some end-of-life routers have this version as the newest and thus are vulnerable at this time. This vulnerability allows for RCE with administrator rights when the administrator visits several pages.
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Analysis
by VulDB Data Team • 02/03/2023
The CVE-2017-15655 vulnerability represents a critical security flaw in the HTTPd server component of Asus asuswrt firmware versions up to 3.0.0.4.376.X, affecting numerous router models that have reached end-of-life status. This vulnerability resides within the web server implementation that handles HTTP requests and responses, specifically targeting buffer overflow conditions that can be exploited by remote attackers to gain complete administrative control over affected devices. The flaw manifests across multiple distinct buffer overflow vectors, each presenting unique exploitation paths while maintaining the same fundamental security weakness. These vulnerabilities are particularly dangerous because they allow for remote code execution with administrator privileges, effectively providing attackers with full control over the affected network devices. The HTTPd server in question serves as the primary interface for web-based administration and configuration of router settings, making it a prime target for exploitation. The vulnerability's impact extends beyond simple privilege escalation, as it enables attackers to manipulate network configurations, intercept traffic, and potentially use the compromised devices as launching points for further attacks within the network infrastructure. The affected firmware versions represent a significant portion of legacy routers that have been discontinued by Asus, leaving users without official security updates or support, thereby creating a persistent security risk for organizations and individuals who continue to operate these devices.
The technical exploitation of CVE-2017-15655 relies on improper input validation within the HTTPd server's handling of web requests, specifically targeting buffer overflow conditions that occur when processing malformed HTTP headers or parameters. These buffer overflows occur due to insufficient bounds checking in string manipulation functions, allowing attackers to write data beyond the allocated memory buffers. The vulnerability is classified as a classic stack-based buffer overflow when processing specific HTTP request parameters, with some variants affecting heap-based memory structures. Attackers can trigger these conditions by sending specially crafted HTTP requests to the router's web interface, which then causes the HTTPd server to execute arbitrary code with the privileges of the web server process. The exploitation requires minimal user interaction, as the vulnerability is triggered when an administrator visits specific web pages within the router's administration interface. This makes the attack particularly insidious because it can be executed without requiring the administrator to actively perform any malicious actions, simply by visiting compromised web pages or following malicious links. The vulnerability's exploitation aligns with ATT&CK technique T1059.007 for remote code execution and T1068 for privilege escalation, while also mapping to CWE-121 for stack-based buffer overflow conditions. The HTTPd server's lack of proper input sanitization creates multiple attack vectors, with each buffer overflow representing a separate entry point for exploitation.
The operational impact of CVE-2017-15655 extends far beyond simple device compromise, as the vulnerability enables attackers to establish persistent access to network infrastructure while potentially using the compromised devices for more sophisticated attacks. Organizations and individuals who continue to operate affected routers face significant risks including data exfiltration, network monitoring, and potential use as botnet nodes for distributed denial-of-service attacks. The vulnerability's ability to grant administrator-level privileges means that attackers can modify firewall rules, redirect traffic, install malicious firmware, or extract sensitive configuration data from the network devices. These compromised routers can serve as stepping stones for lateral movement within networks, allowing attackers to pivot to other connected systems and escalate their access privileges. The vulnerability's exploitation is particularly concerning for enterprise environments where legacy networking equipment may still be in use, as these devices often lack proper network segmentation and security controls. The lack of official security updates for end-of-life devices means that organizations cannot rely on vendor-provided patches, leaving them vulnerable to ongoing exploitation attempts. The vulnerability's impact is amplified by the fact that many organizations continue to use outdated networking equipment that has been discontinued, creating a persistent attack surface that security teams cannot easily address through standard patch management processes.
Mitigation strategies for CVE-2017-15655 require immediate action from affected organizations, as the vulnerability has no legitimate use case and should be addressed through firmware updates or device replacement. The most effective mitigation involves upgrading to firmware version 3.0.0.4.378 or later, which contains the necessary security patches to address all identified buffer overflow conditions. Organizations should conduct comprehensive inventory assessments to identify all affected devices and prioritize their remediation based on network criticality and exposure. Network segmentation and access controls should be implemented to limit exposure of affected devices to untrusted networks, while monitoring systems should be deployed to detect suspicious network traffic patterns that may indicate exploitation attempts. Network administrators should consider disabling unnecessary web-based management interfaces and implementing strict firewall rules to prevent unauthorized access to router administration ports. The vulnerability's exploitation can be detected through network monitoring tools that analyze HTTP traffic patterns and identify malformed requests that attempt to trigger buffer overflow conditions. Security teams should also consider implementing intrusion detection systems with signatures specifically designed to detect exploitation attempts of this vulnerability. In cases where firmware upgrades are not feasible due to device end-of-life status, organizations should consider physical isolation of affected devices or complete removal from production networks. The vulnerability's classification as a critical risk by security vendors and the lack of available patches for end-of-life devices underscores the importance of transitioning away from legacy networking equipment as part of a comprehensive cybersecurity strategy.