CVE-2023-22796 - A Regular Expression Based Denial of Service (DoS) Vulnerability Found in Active Support Versions <6.1.7.1 and <7..4.1

CVE-2023-22796 is a newly discovered security vulnerability impacting certain versions of Active Support, a popular utility framework in the Ruby on Rails ecosystem. The vulnerability is caused by a catastrophic backtracking situation in the regular expression engine when processing a maliciously crafted string input. Because the vulnerability can lead to significant CPU and memory consumption, attackers may exploit it to deny service to affected applications. This article will examine the details of this vulnerability, the affected versions of Active Support, and possible mitigations.

Affected Versions

Active Support versions lower than 6.1.7.1 and 7..4.1 are vulnerable to this CVE-2023-22796 security issue. If you are using an earlier version of Active Support, it is vital to update to the latest patch to minimize your risk.

Exploit Details

The vulnerability lies in the underscore method of Active Support, which is responsible for converting camel-cased strings to snake-cased strings. A specially crafted input string can cause the regular expression engine to enter a state of catastrophic backtracking.

Here's an example of how the issue can occur

def underscore(camel_cased_word)
  word = camel_cased_word.to_s.dup
  # This is a simplified version of the vulnerable regex pattern
  word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2')
end

malicious_input = "A" * 100 + "Za"
underscore(malicious_input)

This malicious_input will trigger extreme performance degradation in the regular expression engine, consuming significant amounts of CPU and memory resources. An attacker can exploit this behavior to potentially cause a denial-of-service condition for the victim's application.

Original References

The CVE-2023-22796 vulnerability was reported and patched recently by the Ruby on Rails team. You can find more information about this vulnerability in the official CVE report and the Rails GitHub repository:

1. CVE report for CVE-2023-22796
2. Rails GitHub Commit for the Patch

Mitigation Steps

To protect your application from the exploitation of this vulnerability, apply these mitigation steps:

1. Upgrade: Update Active Support to versions 6.1.7.1, 7..4.1, or later, to ensure the patched version is in use.
2. Input Validation: Implement input validation on user-supplied data to prevent excessively long and repetitive strings from being processed by the vulnerable method.
3. Monitor: Continuously monitor the application for high CPU and memory usage to quickly detect and mitigate attempts to exploit this vulnerability.

Conclusion

The CVE-2023-22796 vulnerability presents a potential risk to applications using vulnerable versions of Active Support. By being aware of the affected versions, understanding the exploit details, and applying the necessary mitigations, you can secure your application from potential attackers. Regularly staying informed about emerging security vulnerabilities helps ensure your application stays protected from exploitation.

Timeline

Published on: 02/09/2023 20:15:00 UTC
Last modified on: 03/14/2023 08:15:00 UTC