A critical prototype pollution vulnerability, tracked as CVE-2026-34621, has been discovered in Adobe Acrobat and Reader for Windows and macOS. This flaw is actively being exploited in the wild, making it a severe threat to organizations and individuals relying on these widely used PDF tools.
Successful exploitation of this vulnerability could allow an unauthenticated attacker to perform arbitrary code execution on the victim’s machine simply by tricking them into opening a malicious PDF file.
How to check if you’re affected
If you use Adobe Acrobat or Adobe Reader on Windows or macOS, you are likely affected if you haven’t updated your software recently.
- Check Your Version: Open Adobe Acrobat or Reader. Go to Help > About Adobe Acrobat (or Reader). Note the version number.
- Update Immediately: Go to Help > Check for Updates and follow the prompts to install the latest security patches.
- Be Cautious: Avoid opening unsolicited or unexpected PDF files, especially those arriving via email attachments from unknown sources, until your software is fully updated.