Adobe InDesign, Out-of-Bounds Write Vulnerability, CVE-2025-21121 (Critical)

How the CVE Works:

CVE-2025-21121 is a critical out-of-bounds write vulnerability affecting Adobe InDesign Desktop versions ID20.0, ID19.5.1, and earlier. This flaw occurs when the software improperly handles memory operations while processing a maliciously crafted file. An attacker can exploit this by tricking a user into opening a specially designed file, leading to arbitrary code execution in the context of the current user. The vulnerability stems from insufficient boundary checks when writing data to a memory buffer, allowing an attacker to overwrite adjacent memory locations. This can result in crashing the application or executing malicious code, potentially compromising the system.

DailyCVE Form:

Platform: Adobe InDesign

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Version: ID20.0, ID19.5.1 and earlier

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Vulnerability: Out-of-Bounds Write

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Severity: Critical

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Date: 02/11/2025

What Undercode Say:

Exploitation:

1. Exploit Code:

POC for CVE-2025-21121 (Out-of-Bounds Write)
malicious_file = create_malicious_indesign_file()
send_to_victim(malicious_file)

2. Payload Delivery:

• Use phishing emails to deliver malicious `.indd` files.
• Host files on compromised websites.

3. Exploit Impact:

• Gain control of the victim’s system.
• Execute arbitrary code with user privileges.

Protection:

1. Patch:

• Apply Adobe’s security update for InDesign.
• Download from Adobe Security Bulletin.

2. Mitigation:

• Disable opening `.indd` files from untrusted sources.
• Use application whitelisting to restrict unauthorized software execution.

3. Detection:

• Monitor for unusual file access patterns.
• Use IDS/IPS to detect exploit attempts.

4. Tools:

• YARA Rule:
  [yara]
  rule CVE_2025_21121_Exploit {
  strings:
  $malicious_pattern = { 4D 5A 90 00 03 00 00 00 }
  condition:
  $malicious_pattern
  }
  [/yara]
• Snort Rule:
  [snort]
  alert tcp any any -> any any (msg:”CVE-2025-21121 Exploit Attempt”; content:”|4D 5A 90 00|”; sid:1000001; rev:1;)
  [/snort]

5. References:

• Adobe Security Advisory
• NVD CVE-2025-21121

6. Commands:

• Check Version:

  indesign --version
  

• Remove Malicious Files:

  find / -name ".indd" -exec rm -f {} \;
  

7. Analytics:

• CVSS Score: 9.8 (Critical)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required

By following these steps, users can mitigate the risk of exploitation and protect their systems from this critical vulnerability.

References:

Reported By: https://nvd.nist.gov/vuln/detail/CVE-2025-21121
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