CVE-2015-9239: Regular Expression Denial of Service in ansi2html

Background

The ansi2html package is a Node.js module that converts ANSI escape codes to HTML. It has been widely used for formatting and displaying colored text in terminal applications. However, the package is vulnerable to a regular expression denial of service (ReDoS) attack when certain types of user input are passed in.

Vulnerability Detail

The regular expression used in the ansi2html package is susceptible to ReDoS, which occurs when an attacker provides specially crafted input that causes the regular expression matching to take an excessive amount of time. This can lead to a denial of service (DoS) condition, where the application becomes unresponsive or crashes.

The vulnerability affects all versions of ansi2html and has not been addressed for four years. To mitigate the risk, it is recommended to avoid passing user input to the package or limit the size of the input string. However, even with input size limitations, the match time can still grow significantly, making it challenging to find a balance between usability and protection against the attack.

As a workaround, it is advised to consider using an alternative module that is actively maintained and provides similar functionality. Several alternative modules are available on npm.

Workaround

To mitigate the vulnerability in ansi2html, it is advised to avoid passing user input to the package or limit the size of the input string. However, this may impact the usability of the application, as the match time of the regular expression grows significantly even with small increases in input size. As a more robust solution, consider using an alternative module that is actively maintained and provides similar functionality. Here's an example of how to use the ansi-html module as an alternative:

var ansiHTML = require('ansi-html');

var input = '[1111111111111111111111;0000000000000000000000';
var output = ansiHTML(input);
console.log(output);

This code snippet demonstrates the usage of the ansi-html module to convert ANSI escape codes to HTML. It is important to note that the ansi-html module is just one of the available alternatives and may require additional configuration or adjustments depending on the specific use case.

Conclusion

The ansi2html package is vulnerable to a regular expression denial of service (ReDoS) attack, which can lead to a denial of service (DoS) condition in applications using the package. To mitigate the risk, it is advised to avoid passing user input to the package or limit the size of the input string. However, the match time of the regular expression grows significantly even with small increases in input size, making it challenging to find a balance between usability and protection against the attack. It is recommended to transition to an alternative module that is actively maintained and provides similar functionality. Thorough testing and validation should be performed when integrating the new module into the existing codebase.

For further support on vulnerability remediation, please contact DevNack.com.

See every vulnerability recorded for ansi2html →

FAQ