CVE-2017-16114 in marked
Summary
by MITRE
The marked module is vulnerable to a regular expression denial of service. Based on the information published in the public issue, 1k characters can block for around 6 seconds.
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Analysis
by VulDB Data Team • 03/21/2023
The marked module represents a popular JavaScript library used for template processing and content generation within web applications. This vulnerability manifests as a regular expression denial of service attack that exploits inefficient pattern matching algorithms. The flaw occurs when the module processes input strings containing carefully crafted regular expressions that trigger catastrophic backtracking behavior in its underlying parsing engine. The vulnerability specifically affects versions of the marked module prior to 0.3.6 where proper input validation and regex optimization were not implemented.
The technical implementation of this vulnerability relies on the module's use of regular expressions to parse markdown syntax elements such as links, code blocks, and other formatting constructs. When malicious input containing nested quantifiers or alternation patterns is processed, the regular expression engine enters a state of exponential time complexity where it must evaluate an enormous number of possible matching paths. The vulnerability demonstrates that with just 1000 characters of specially crafted input, the processing time can escalate to approximately six seconds, effectively creating a denial of service condition that can be exploited by attackers to consume system resources and disrupt service availability.
From an operational perspective, this vulnerability presents significant risk to web applications that utilize the marked module for processing user-generated content or markdown input. Attackers can leverage this weakness to perform resource exhaustion attacks against servers, potentially causing cascading failures in applications that rely on the module for content rendering. The impact extends beyond simple service disruption as it can be used in conjunction with other attack vectors to create more sophisticated denial of service scenarios. The vulnerability operates at the application layer and can be particularly dangerous in environments where the marked module is used in conjunction with other vulnerable components, creating opportunities for attackers to escalate their impact.
Security practitioners should implement immediate mitigations including upgrading to marked version 0.3.6 or later where the vulnerability has been patched through improved regex pattern validation and input sanitization. The fix typically involves implementing proper bounds checking on regular expression patterns and limiting the complexity of patterns that can be processed. Organizations should also consider implementing rate limiting and input validation at the application level to prevent malicious inputs from reaching the vulnerable parsing functions. This vulnerability aligns with CWE-400 which categorizes regular expression denial of service attacks, and can be mapped to ATT&CK technique T1499.004 for resource exhaustion attacks. Additionally, implementing proper monitoring and alerting for unusual processing times or resource consumption patterns can help detect exploitation attempts. The remediation process should include thorough code review to identify any other instances where similar regex patterns might be used in the application stack, ensuring comprehensive protection against similar vulnerabilities.