CVE-2015-3295 in markdown-it
Summary
by MITRE
markdown-it before 4.1.0 does not block data: URLs.
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Analysis
by VulDB Data Team • 12/08/2022
The vulnerability identified as CVE-2015-3295 affects the markdown-it library version 4.1.0 and earlier, presenting a significant security risk through improper handling of data URLs within markdown processing. This issue stems from the library's failure to adequately sanitize or block data URLs, which can contain malicious payloads that execute unintended operations when processed by applications using this markdown parser.
The technical flaw manifests in the markdown-it library's URL validation mechanism, which does not properly filter or reject data URLs that begin with the data: scheme. These URLs can contain embedded content such as base64 encoded scripts, images, or other resources that bypass normal security controls. When markdown-it processes markdown content containing such URLs, it may inadvertently render or execute the embedded data, creating potential attack vectors for malicious actors.
This vulnerability operates under the broader context of insecure input handling and improper sanitization, aligning with CWE-20 which addresses "Improper Input Validation" and CWE-116 which covers "Improper Encoding or Escaping of Output." The flaw represents a classic example of how seemingly benign parsing operations can become security risks when input validation is insufficient. The impact is particularly severe in web applications where markdown content is user-generated, as attackers can craft malicious markdown that executes arbitrary code when rendered.
The operational impact of CVE-2015-3295 extends beyond simple XSS attacks, potentially enabling more sophisticated exploitation techniques including phishing, credential theft, and privilege escalation attacks. When applications using vulnerable versions of markdown-it process untrusted markdown content, they become susceptible to attacks that can compromise user sessions, steal sensitive data, or provide attackers with persistent access to affected systems. This vulnerability particularly affects web applications, content management systems, and any platform that allows users to submit markdown-formatted content.
Organizations should immediately upgrade to markdown-it version 4.1.0 or later to mitigate this vulnerability, as this release includes proper URL filtering mechanisms that prevent data URLs from being processed. Additional mitigations include implementing comprehensive input validation at multiple layers, deploying web application firewalls that can detect and block data URL patterns, and conducting thorough security testing of markdown processing components. The ATT&CK framework categorizes this vulnerability under T1203 "Exploitation for Client Execution" and T1059 "Command and Scripting Interpreter" as attackers can leverage the vulnerability to execute malicious commands through crafted markdown content. Security teams should also consider implementing content security policies that restrict data URL usage and regularly audit their markdown processing pipelines for similar vulnerabilities.