CVE-2017-17461 in npm
Summary
by MITRE
A Regular expression Denial of Service (ReDoS) vulnerability in the file marked.js of the marked npm package (tested on version 0.3.7) 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 • 01/26/2021
The vulnerability identified as CVE-2017-17461 represents a critical Regular Expression Denial of Service (ReDoS) flaw within the marked npm package version 0.3.7. This issue specifically affects the marked.js file which serves as a markdown parser implementation. The vulnerability stems from the package's handling of regular expressions during markdown parsing operations, creating an exploitable condition that can be leveraged by remote attackers to cause system resource exhaustion.
The technical flaw manifests through the use of inefficient regular expressions that are susceptible to catastrophic backtracking when processing maliciously crafted input strings. When the marked package processes markdown content containing specially constructed regular expression patterns, the parsing engine enters into an exponential time complexity scenario where the regular expression engine attempts to match the input against the pattern through numerous backtracking iterations. This behavior is characteristic of ReDoS vulnerabilities and aligns with CWE-1333 which specifically addresses regular expression matching issues leading to resource exhaustion. The vulnerability operates by crafting input strings that cause the regular expression engine to perform an excessive number of operations, ultimately consuming all available CPU resources and leading to service disruption.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential system compromise and availability degradation. Remote attackers can exploit this weakness by submitting malicious markdown content to applications that utilize the marked package, causing servers to become unresponsive or crash entirely. The attack vector is particularly dangerous because it requires minimal privileges and can be executed through standard input processing mechanisms. Systems relying on the marked package for markdown rendering, including web applications, content management systems, and documentation generators, become vulnerable to this attack. The vulnerability affects any environment where user-supplied markdown content is processed without proper input sanitization, creating a widespread risk across numerous applications and services.
Mitigation strategies for CVE-2017-17461 involve immediate package updates to versions that address the regular expression vulnerability, typically through patch releases that either fix the problematic regex patterns or implement input validation measures. Organizations should implement comprehensive input validation and sanitization procedures that filter or reject suspicious markdown content before processing. The use of rate limiting and resource monitoring can help detect and prevent exploitation attempts. Additionally, implementing proper security controls such as web application firewalls and input validation layers can provide additional protection against ReDoS attacks. This vulnerability also highlights the importance of adhering to security best practices including regular dependency updates, security scanning of npm packages, and implementing proper threat modeling for applications that process untrusted input. The ATT&CK framework categorizes this as a resource exhaustion technique under the T1499 sub-technique, emphasizing the need for robust input validation and processing controls to prevent such attacks from compromising system availability.