CVE-2021-42734: Unmasking the Out-of-Bounds Read Vulnerability in Adobe Photoshop Version 22.5.1 and Earlier Versions

Abstract: Adobe Photoshop, a widely-used photo editing software, faces a critical out-of-bounds read vulnerability affecting version 22.5.1 and earlier versions. This vulnerability (CVE-2021-42734) may lead to exposure of sensitive memory information and potentially help an attacker bypass crucial security measures such as Address Space Layout Randomization (ASLR). Exploiting this vulnerability, however, requires user interaction, as the victim must open a malicious file.

Introduction

Adobe Photoshop, one of the most popular photo editing tools in the world, is grappling with an out-of-bounds read vulnerability. This vulnerability has been assigned the CVE-2021-42734 identifier and impacts Adobe Photoshop version 22.5.1 and earlier. The issue could disclose sensitive memory information, putting users' data at risk, and possibly allow attackers to circumvent security mitigations, most notably the Address Space Layout Randomization (ASLR).

To exploit this vulnerability, an attacker must trick the victim into opening a malicious file. As such, the attack vector relies heavily on user interaction, making it crucial for users to stay vigilant and avoid opening files from untrusted sources.

Code Snippet

The vulnerability pertains to an out-of-bounds read issue, which occurs due to Adobe Photoshop reading data beyond the intended buffer boundary. A code snippet illustrating this vulnerability might resemble the following example:

#include <stdio.h>

int main() {
  int arr[] = {10, 20, 30, 40};
  int n = 5;
  int i;
  for(i = ; i < n; i++) {
    printf("%d", arr[i]); // out-of-bounds read at i = 4
  }
  return ;
}

This code snippet demonstrates an unintended buffer boundary read due to incorrect loop bounds (i.e., the variable n should be 4 instead of 5). While this is a simplified example, it highlights the nature of an out-of-bounds read vulnerability in a program.

Original References

Adobe publicly acknowledged the vulnerability in its security advisories. You can access the original documents through the following links:

1. Adobe Security Bulletin – APSB21-89
2. NIST National Vulnerability Database – CVE-2021-42734

Exploit Details

As mentioned earlier, exploiting this vulnerability requires user interaction. A potential exploit scenario might involve the following steps:

1. The attacker creates a malicious file (e.g., a PSD or TIFF file) that triggers the out-of-bounds read vulnerability in Adobe Photoshop.
2. The attacker sends this file to the victim through email, file sharing platform, or any other online medium.

The victim downloads and opens the malicious file using Adobe Photoshop.

4. The vulnerability is exploited, leading to the potential disclosure of sensitive memory information. Furthermore, it may provide the attacker with enough data to bypass ASLR, thereby making subsequent attacks more potent.

Closing Thoughts

To prevent exploitation of this vulnerability, users should update their Adobe Photoshop software to the latest version, which contains the necessary patches to address this issue. In the meantime, users must exercise caution when opening files from unfamiliar sources to minimize the risk of falling victim to an attack leveraging this vulnerability (CVE-2021-42734).

Timeline

Published on: 09/07/2023 13:15:00 UTC
Last modified on: 09/07/2023 13:42:00 UTC