CVE-2015-8854 in marked Package
Summary
by MITRE
The marked package before 0.3.4 for Node.js allows attackers to cause a denial of service (CPU consumption) via unspecified vectors that trigger a "catastrophic backtracking issue for the em inline rule," aka a "regular expression denial of service (ReDoS)."
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2015-8854 affects the marked package version 0.3.3 and earlier in the Node.js ecosystem, representing a critical security flaw that enables attackers to execute denial of service attacks through carefully crafted input. This issue stems from a regular expression denial of service (ReDoS) vulnerability specifically within the em inline rule of the marked markdown parser. The vulnerability manifests when the parser encounters maliciously constructed markdown input that triggers catastrophic backtracking in its regular expression patterns, leading to excessive cpu consumption and system resource exhaustion. The marked package serves as a popular markdown rendering library in Node.js applications, making this vulnerability particularly dangerous as it can be exploited across numerous web applications and services that rely on markdown processing.
The technical implementation of this vulnerability involves the exploitation of regular expression patterns that contain inefficient backtracking behavior. When the em inline rule processes certain input sequences, the regular expression engine enters a state where it must evaluate an exponential number of possible matching paths, causing the cpu utilization to spike dramatically. This behavior aligns with the common characteristics of ReDoS attacks as defined by the Common Weakness Enumeration (CWE-400) under weakness category 400, which specifically addresses denial of service vulnerabilities related to input processing. The catastrophic backtracking occurs because the regular expression pattern does not properly handle input sequences that would cause the engine to perform redundant computations, leading to a quadratic or exponential growth in processing time as input length increases.
The operational impact of CVE-2015-8854 extends beyond simple service disruption, as it can effectively render affected applications unusable and potentially impact system availability at scale. Attackers can craft malicious markdown content that when processed by vulnerable applications causes the system to consume excessive cpu resources, leading to application hangs, slow response times, or complete service unavailability. This vulnerability is particularly concerning in web applications where user input is processed through the marked parser, as it can be exploited through various attack vectors including comment fields, content management systems, or any interface that accepts markdown input. The attack can be executed with minimal resources and can cause cascading failures in systems that rely on the marked package for content processing, making it a preferred vector for resource exhaustion attacks in Node.js environments.
Mitigation strategies for this vulnerability require immediate patching of the marked package to version 0.3.4 or later, which contains the necessary regular expression optimizations to prevent catastrophic backtracking. Organizations should implement comprehensive input validation and sanitization measures that filter out potentially malicious content before it reaches the markdown parser, although this approach is less reliable than proper patching. Security teams should also consider implementing rate limiting and resource monitoring to detect and prevent exploitation attempts, particularly in environments where untrusted input is processed. The vulnerability demonstrates the importance of regular security audits and dependency management in Node.js applications, as it highlights how seemingly benign parsing libraries can become attack vectors. From an ATT&CK framework perspective, this vulnerability maps to technique T1499.004 for resource exhaustion and T1211 for privilege escalation through service disruption, emphasizing the need for robust input validation and proper security controls to prevent exploitation of such parsing vulnerabilities.