In this post, we will be discussing and analyzing a significant vulnerability, CVE-2022-30973, caused by the failure to apply the fix for CVE-2022-30126 to the 1.x branch in the 1.28.2 release of Apache Tika. This vulnerability could lead to a denial of service (DoS) attack through backtracking in a specially crafted file. We will delve into the code snippet, provide links to original references, and discuss the exploit details to help users grasp the issue and implement the appropriate fix.

Vulnerability Details

In Apache Tika's 1.28.2 release, a regular expression in the StandardsText class, used by the StandardsExtractingContentHandler, has led to a possible denial of service (DoS) caused by backtracking in a specific crafted file. The DoS attack may impact systems running the StandardsExtractingContentHandler, which is a non-standard handler. Despite the fix for CVE-2022-30126, the oversight in applying the patch to the 1.x branch has resulted in this vulnerability. Thankfully, this issue is addressed in the 1.28.3 release.

Code Snippet

The vulnerability stems from the use of a regular expression in the StandardsText class. Here is an example of a problematic regex:

  String regex = "(?s)(<sometag>.*?</sometag>)";
  String maliciousFileContent = "<sometag>" + "a" * 100000 + "</maliciousBrackets>";
  String input = Pattern.compile(regex).matcher(maliciousFileContent).matches();

In this sample, the regex is designed to match the opening and closing "sometag" tags in a text. However, when it is used on the maliciousFileContent string created with a large number of "a" characters and an incorrect closing tag, the regex engine starts backtracking, causing a significant delay and leading to a denial of service.

Exploit Details

An attacker can exploit CVE-2022-30973 by constructing a carefully crafted document containing a complex regular expression that leads to excessive backtracking. When processed by the StandardsExtractingContentHandler, the regex engine will consume a considerable amount of resources (mainly CPU and memory) trying to match the pattern, leading to a denial of service attack that may disrupt the system's normal functioning.

Solutions & Mitigations

To resolve this vulnerability, users are advised to update their Apache Tika installations to version 1.28.3, where the fix for CVE-2022-30126 has been correctly applied to the 1.x branch. The updated version does not have the vulnerability and is safe to use.

If upgrading to 1.28.3 is not immediately possible, users can also consider disabling the StandardsExtractingContentHandler temporarily or employing alternative handlers not affected by the vulnerability.

Original References

For more information about this vulnerability and the associated fix, here are some links to official references:

1. Apache Tika Release Notes: https://tika.apache.org/1.28.3/release_notes.html
2. CVE-2022-30973 Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-30973
3. CVE-2022-30126 Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-30126

Conclusion

The CVE-2022-30973 vulnerability in Apache Tika's 1.x branch is a vital example of the importance of keeping libraries and software updated with the latest security fixes. By applying the fix for CVE-2022-30126 in the 1.28.3 release or taking precautionary measures, users can protect their systems from potential denial-of-service attacks caused by this particular vulnerability.

Timeline

Published on: 05/31/2022 14:15:00 UTC
Last modified on: 07/22/2022 19:15:00 UTC