CVE-2024-7866

What it actually does

A malformed PDF containing a circular object reference inside a pattern resource triggers unbounded recursion during parsing, exhausting the call stack and causing a crash.

Why it matters to the business

Processing untrusted PDF files can crash document viewers or conversion tools, interrupting workflows that rely on PDF handling and requiring manual restarts or recovery.

How an attack unfolds

An attacker creates a PDF with a self-referential loop in a pattern dictionary. When the file is opened in a vulnerable parser, the pattern resource handler recurses indefinitely until the stack is exhausted and the process terminates.

How to fix it

Upgrade Xpdf to a version newer than 4.05 that eliminates the recursive pattern handling flaw.

How to confirm the fix worked

Reprocess a previously crashing test PDF after the upgrade and confirm the application remains stable without stack overflow.

Typical attack path

1. Generate PDF with circular pattern object references
2. Distribute the crafted file via email, web download, or shared storage
3. Victim opens the document with the affected PDF viewer or library
4. Parser enters infinite recursion on the pattern resource and crashes

How to detect it

Review application crash logs and core dumps for stack exhaustion events immediately following PDF open attempts; correlate with file creation or download timestamps of suspicious PDFs.

What your security team should do

• Apply the newest Xpdf release across all endpoints that render PDFs
• Replace or sandbox any remaining instances of the vulnerable version
• Add PDF processing to the inventory of memory-safety-sensitive components