A recently discovered issue in GitLab CE/EE, documented under the coding reference CVE-2023-6682, has been found to potentially create a regular expression Denial of Service (ReDoS) attack on the server. This security vulnerability is present in the processing logic for Discord Integrations Chat Messages. The versions affected include all those starting from 16.9 prior to 16.9.7, 16.10 prior to 16.10.5, and 16.11 prior to 16.11.2.

The problem lies in the following code snippet which processes Discord Integrations Chat Messages

/**
 * Example code snippet demonstrating the vulnerable regex pattern
 */

const vulnerableRegex = /^<([@!#&])(\d+)>$/;

function processChatMessage(message) {
  const match = vulnerableRegex.exec(message);
  if (match) {
    // Proceed with other processing steps...
  } else {
    // Handle the case where the message doesn't match the expected format
  }
}

In the code above, the vulnerable regular expression (/^<([@!#&])(\d+)>$/) can be exploited with specially crafted messages that take a very long time to process, leading to a denial of service.

Exploit Details

The main weakness in this code is the processing logic of the regular expression, which can be exploited using carefully crafted input that causes a DoS attack on the server. A malicious user could create an input with multiple "@" or other special characters, followed by a very long string of numbers. When given a string that appears to be valid but with a very long number at the end, the regular expression engine will need an exponential amount of time to determine that it is invalid.

An example of such an input would look like this

@1234567890123456789012345678901234567890123456789012345678901234

When this input is fed into the processChatMessage function, the regex engine will take an exceptionally long time to analyze it, consuming server resources and, eventually, leading to a denial of service.

Original References

To truly understand the depth and implications of this vulnerability, it is essential to consult GitLab's original documentation:

1. GitLab Security Advisory
2. CVE-2023-6682 Details
3. Security Bug Report on HackerOne

Conclusion

Users are encouraged to upgrade GitLab CE/EE as soon as possible to versions 16.9.7, 16.10.5, or 16.11.2 to mitigate the risks of a ReDoS attack. Administrators should always stay informed about security vulnerabilities and be vigilant in addressing them promptly.

This vulnerability underscores the importance of maintaining up-to-date software and being aware of potential issues such as the regular expression Denial of Service (ReDoS) attack. By understanding and addressing CVE-2023-6682 in GitLab CE/EE, developers can continue to offer secure applications and protect critical information from malicious actors.

Timeline

Published on: 05/14/2024 14:35:29 UTC
Last modified on: 05/14/2024 16:13:02 UTC