Regular Expression Denial of Service in markdown

Background

The markdown package is an npm package used for converting Markdown syntax to HTML. It provides a convenient way to parse and render Markdown content. However, all versions of markdown are vulnerable to Regular Expression Denial of Service (ReDoS). The vulnerability specifically affects the markdown.toHTML() function, which exhibits degraded performance when parsing long strings containing underscores. This can potentially lead to a Denial of Service if the parser accepts user input.

Vulnerability Detail

The Regular Expression Denial of Service (ReDoS) vulnerability in the markdown package arises from inefficient regular expressions used in the markdown.toHTML() function. When processing long strings with underscores, the regular expressions can cause the function to exhibit significantly degraded performance. This can be exploited by an attacker to craft malicious input that triggers a ReDoS attack, leading to a denial of service condition. The severity of this vulnerability is considered low.

Workaround

As there is no fix available, a possible workaround is to sanitize user input before passing it to the markdown.toHTML() function. This can involve validating and limiting the length of input strings, as well as removing any potentially malicious characters or patterns. Here is an example of how to sanitize user input in JavaScript:

function sanitizeInput(input) {
  // Validate and limit input length
  if (input.length > MAX_LENGTH) {
    throw new Error('Input length exceeds maximum limit');
  }

  // Remove underscores
  const sanitizedInput = input.replace(/_/g, '');

  return sanitizedInput;
}

Conclusion

The markdown package is vulnerable to a Regular Expression Denial of Service (ReDoS) issue, which can lead to a denial of service if user input is accepted by the markdown.toHTML() function. Currently, there is no fix available, and it is recommended to use an alternative package until a fix is released. Sanitizing user input can help mitigate the risk of this vulnerability. For further support on vulnerability remediation, you can reach out to DevNack.com.

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