CVE-2015-1370 in marked
Summary
by MITRE
Incomplete blacklist vulnerability in marked 0.3.2 and earlier for Node.js allows remote attackers to conduct cross-site scripting (XSS) attacks via a vbscript tag in a link.
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Analysis
by VulDB Data Team • 04/12/2022
The vulnerability identified as CVE-2015-1370 represents a critical security flaw in the marked JavaScript markdown parser version 0.3.2 and earlier, which is widely used in Node.js environments. This issue manifests as an incomplete blacklist implementation that fails to properly sanitize user input containing malicious script tags. The vulnerability specifically targets the parser's handling of vbscript tags within link elements, creating a pathway for remote attackers to execute cross-site scripting attacks against unsuspecting users who encounter the maliciously crafted markdown content. The flaw stems from the parser's insufficient filtering mechanism that does not adequately block potentially dangerous scripting content, particularly within HTML attributes where vbscript handlers could be embedded.
The technical implementation of this vulnerability exploits the marked parser's incomplete security model that relies on blacklisting specific dangerous elements rather than implementing proper input validation or sanitization. When the parser encounters a link containing a vbscript tag, it fails to properly neutralize or remove the malicious content, allowing the script to execute within the context of a victim's browser session. This particular weakness aligns with CWE-79, which describes improper neutralization of input during web page generation, commonly known as cross-site scripting. The vulnerability demonstrates how a simple oversight in input filtering can create a significant attack surface, particularly in applications that process untrusted user input through markdown rendering.
The operational impact of CVE-2015-1370 extends beyond simple XSS execution, as it enables attackers to potentially steal user sessions, deface websites, redirect users to malicious domains, or perform other malicious activities within the victim's browser context. Applications utilizing the affected marked versions in environments where users can submit markdown content, such as comment systems, wiki platforms, or content management systems, become vulnerable to these attacks. The remote nature of the exploit means that attackers can craft malicious markdown content and deliver it through various channels without requiring local access to the target system, making this vulnerability particularly dangerous in web applications where user-generated content is prevalent. This vulnerability also relates to ATT&CK technique T1203, which covers "Exploitation for Client Execution" through web-based attack vectors.
Mitigation strategies for this vulnerability require immediate action including upgrading to marked version 0.3.3 or later, which contains the necessary fixes for the blacklist implementation. Organizations should also implement additional security measures such as content security policies to limit script execution, input validation at multiple layers, and comprehensive security testing of markdown rendering components. The fix addresses the core issue by implementing more robust sanitization routines that properly handle vbscript and other potentially dangerous script handlers, ensuring that all malicious content is neutralized before content is rendered to end users. Security teams should conduct thorough vulnerability assessments of all systems using marked parser versions prior to the fix to identify potential exploitation vectors and implement appropriate compensating controls.