CVE-2022-37052 - Poppler 22.07. Reachable Object::getString Assertion Causing Denial of Service

In Poppler 22.07., a reachable Object::getString assertion occurs, allowing attackers to cause a denial of service due to a markObject failure. Poppler is a widely used PDF rendering library with support for various languages and platforms. This vulnerability poses a risk to users who handle PDF files and can be exploited by maliciously crafted documents. In this post, we will discuss the technical details of this vulnerability, provide code snippets, and offer links to original references.

Technical Details

The vulnerability stems from a reachable Object::getString assertion within the Poppler 22.07. library. The affected code snippet is as follows:

if (markObject(xRef)) {
  if (obj->isStream()) {
    obj = obj->streamGetDict();
  }
  if (obj->isDict()) {
    ...
  } else {
    assert(obj->isNullOrNone() || arrayIndex >= );
    success = false;
  }
}

As seen in the code snippet, the markObject(xRef) function checks if an object is marked as visited. A potential bug arises when the object’s associated dictionary is not validated, leading to a reachable assertion. This assertion eventually results in a denial of service attack.

Exploit Details

To exploit this vulnerability, an attacker needs to craft a malicious PDF document designed specifically to trigger the Object::getString assertion in the vulnerable Poppler library. When a user opens the crafted PDF with an application using the vulnerable version of Poppler, the assertion will be encountered, causing the application to crash and denying the user access to their PDF file.

As an example, consider a scenario where a user receives an email with a seemingly legitimate PDF file attached. Upon opening the file, the user’s PDF viewer, which utilizes the vulnerable Poppler library, crashes due to the reachable Object::getString assertion. This exploit effectively denies the user access to their document and potentially disrupts their workflow, resulting in a successful denial of service attack.

Mitigation and Recommendations

To mitigate this vulnerability, users should update their Poppler library to a version beyond 22.07., as future revisions are expected to incorporate patches addressing this issue. Additionally, users should exercise caution when downloading and opening PDF files from untrusted sources.

For more information about CVE-2022-37052, refer to the following resources

1. CVE Details (https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-37052)
2. National Vulnerability Database (NVD) (https://nvd.nist.gov/vuln/detail/CVE-2022-37052)
3. Poppler Git Repository (https://gitlab.freedesktop.org/poppler/poppler)

Conclusion

In conclusion, the reachable Object::getString assertion vulnerability in Poppler 22.07. is a serious issue that allows attackers to cause a denial of service. Users should ensure that they are using the latest version of the Poppler library and remain vigilant when handling PDF files from untrusted sources. By taking proactive steps to stay informed about security risks and applying appropriate patches, users can effectively protect themselves from potential exploits.

Timeline

Published on: 08/22/2023 19:16:00 UTC
Last modified on: 08/25/2023 20:17:00 UTC