CVE-2023-26418: Critical Use After Free Vulnerability in Adobe Acrobat Reader Leading to Arbitrary Code Execution

A critical security vulnerability, classified under the identifier CVE-2023-26418, has been discovered in Adobe Acrobat Reader. Affected versions include 23.001.20093 (and earlier) and 20.005.30441 (and earlier). This vulnerability is caused by a Use After Free (UAF) error that could lead to arbitrary code execution in the context of the current user. Successful exploitation of this issue requires user interaction, as a targeted victim must open a malicious file.

In this post, we will discuss the details of the vulnerability, describe the exploit process, and provide various resources that help understand and mitigate the threat.

Vulnerability Details

A Use After Free vulnerability occurs when an application continues to use a memory object after it has been freed (released) by the program. The vulnerability in Adobe Acrobat Reader stems from illegal use of a certain memory object in the application, which can be leveraged by an attacker to execute arbitrary code without the user's knowledge.

The CVE-2023-26418 vulnerability has a CVSS v3.1 score of 8.8, indicating a critical severity level.

Exploit Details

To exploit the vulnerability, an attacker must craft a malicious PDF file that contains embedded objects designed to trigger the Use After Free error. When the victim opens the malicious file using the vulnerable Adobe Acrobat Reader, the embedded objects cause the application to access the freed memory object. This subsequently opens the door for the attacker to execute their arbitrary code in the context of the current user.

This exploit relies on social engineering, as it needs the target user to interact with the malicious file. Attackers could use phishing emails, file-sharing platforms, or compromised websites to spread the malicious PDF.

Code Snippet

While we do not provide actual exploit code for ethical reasons, below is a conceptual demonstration of the vulnerability in pseudocode.

// Malicious embedded object
class BadObject {
  function trigger_UAF(){
    // Code that causes UAF
  }
}

// Victim opens the malicious PDF
open_malicious_PDF(){
  bad_object_instance = new BadObject()
  bad_object_instance.trigger_UAF()
  // At this point, the UAF is triggered, and the attacker can execute arbitrary code
}

Adobe Security Bulletin: APSB21-62

https://helpx.adobe.com/security/products/acrobat/apsb21-62.html

CVE-2023-26418 - NIST National Vulnerability Database

https://nvd.nist.gov/vuln/detail/CVE-2023-26418

Mitigation

Adobe has released updates addressing this vulnerability in its security bulletin APSB21-62. Users are urged to update their Adobe Acrobat Reader application to the latest version to safeguard against potential exploitation.

Additionally, it's essential for users to exercise caution while handling files from unknown sources, especially when opening email attachments or downloading files from untrusted websites.

Conclusion

CVE-2023-26418 highlights the potential severity of Use After Free vulnerabilities in widely-used software like Adobe Acrobat Reader. It serves as a reminder for users to remain vigilant of social engineering tactics employed by attackers and the importance of keeping software up to date with the latest security patches.

Timeline

Published on: 04/12/2023 21:15:00 UTC
Last modified on: 04/21/2023 01:34:00 UTC