CVE-2016-10703 in npm
Summary
by MITRE
A regular expression Denial of Service (DoS) vulnerability in the file lib/ecstatic.js of the ecstatic npm package, before version 2.0.0, allows a remote attacker to overload and crash a server by passing a maliciously crafted string.
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Analysis
by VulDB Data Team • 01/18/2023
The CVE-2016-10703 vulnerability represents a critical regular expression denial of service flaw within the ecstatic npm package, specifically affecting versions prior to 2.0.0. This vulnerability resides in the lib/ecstatic.js file and demonstrates how seemingly innocuous input processing can become a vector for catastrophic system failure. The ecstatic package serves as a static file server for node.js applications, making this vulnerability particularly dangerous as it can impact any application relying on this middleware for serving static content. The flaw manifests when the package processes file paths through regular expressions that are susceptible to catastrophic backtracking, a well-documented vulnerability pattern that can cause exponential execution time growth with malicious input.
The technical implementation of this vulnerability exploits the inherent weakness in how regular expressions handle certain input patterns that trigger backtracking behavior. When a maliciously crafted string is passed to the file processing logic, the regular expression engine enters into a state where it must evaluate exponentially increasing numbers of possible matching paths. This creates a situation where a relatively short input string can cause the system to consume excessive computational resources, leading to complete service unavailability. The vulnerability aligns with CWE-400, which specifically addresses the improper handling of regular expressions that can lead to resource exhaustion. The attack vector is particularly insidious because it requires no authentication or specialized privileges, making it accessible to any remote attacker who can send requests to the affected server.
The operational impact of CVE-2016-10703 extends far beyond simple service disruption, as it represents a fundamental security weakness that can be exploited to bring entire web applications to their knees. Servers running affected versions of the ecstatic package become vulnerable to sustained denial of service attacks where a single malicious request can cause the server process to consume all available CPU resources, effectively rendering the application unusable to legitimate users. This vulnerability directly maps to ATT&CK technique T1499.004, which covers network denial of service attacks, and can be leveraged as part of broader attack campaigns targeting availability. The widespread adoption of the ecstatic package in node.js environments means that numerous applications across different sectors could be simultaneously compromised, creating cascading effects that extend beyond individual applications to impact entire service ecosystems.
Mitigation strategies for this vulnerability require immediate attention and systematic implementation across affected systems. The primary and most effective solution involves upgrading to version 2.0.0 or later of the ecstatic package, which includes fixed regular expression patterns that eliminate the backtracking vulnerability. Organizations should conduct comprehensive inventory audits to identify all applications using vulnerable versions of the package and implement automated monitoring for dependency updates. Network-level protections can include rate limiting and input validation at proxy layers to prevent malicious requests from reaching vulnerable servers, though these measures provide only temporary relief. The vulnerability also highlights the importance of regular security audits and dependency management practices, as highlighted in industry standards such as NIST SP 800-160, which emphasizes the need for secure software development practices. Additionally, implementing proper input sanitization and validation at multiple layers of the application architecture can provide defense-in-depth protection against similar vulnerabilities in other components.