CVE-2020-13557

What it actually does

Use-after-free in the JavaScript engine allows reuse of freed memory, enabling arbitrary code execution when a malicious PDF is processed.

Why it matters to the business

Attackers can gain full control of user systems by delivering malicious PDFs via email or websites, leading to data theft, ransomware deployment, or persistent access across the organization.

How an attack unfolds

An attacker crafts a PDF that triggers reuse of freed memory in the JavaScript engine. The file is delivered through email or a website; when opened in Foxit Reader, or when a malicious site is visited with the browser plugin enabled, the vulnerability executes attacker-controlled code.

How to fix it

Upgrade Foxit Reader to the latest version that resolves the use-after-free issue. Disable the browser plugin extension if it is not required. Apply vendor patches as soon as they become available.

How to confirm the fix worked

Confirm the installed Foxit Reader version is newer than 10.1.0.37527 and test that previously crashing sample PDFs no longer trigger code execution or memory reuse.

Typical attack path

1. Craft a PDF that triggers the use-after-free condition in the JavaScript engine
2. Host or send the malicious PDF to the target user
3. Victim opens the PDF in Foxit Reader or visits a malicious site with the browser plugin enabled
4. Arbitrary code executes with the privileges of the Reader process

How to detect it

Review application crash logs and process creation events around PDF file opens; look for Foxit Reader spawning unexpected child processes or loading unusual modules after PDF handling.

What your security team should do

• Immediately update all Foxit Reader installations to a patched release
• Disable the browser plugin extension unless explicitly needed
• Block or sandbox PDF attachments from untrusted sources
• Monitor for unexpected Foxit Reader crashes or child process creation