CVE-2024-2971

What it actually does

Out-of-bounds array write triggered during PDF parsing when an indirect reference contains a negative object number, resulting in memory corruption within the Xpdf engine.

Why it matters to the business

Low-probability denial-of-service or application instability on systems that process untrusted PDF files with vulnerable Xpdf versions; limited operational impact due to local attack vector and high complexity.

How an attack unfolds

An attacker creates a specially crafted PDF containing an indirect object reference with a negative object number. When Xpdf parses the file, the negative value is used as an array index without proper bounds checking, causing an out-of-bounds write.

How to fix it

Upgrade Xpdf to the latest version that resolves the negative object number handling issue in PDF indirect references.

How to confirm the fix worked

Confirm Xpdf version exceeds 4.05; test parsing of a minimal PDF containing a negative indirect object reference to verify absence of crash or corruption.

Typical attack path

1. Craft malicious PDF embedding indirect reference with negative object number
2. Deliver PDF to target via email, download, or file share
3. Victim opens PDF using vulnerable Xpdf 4.05 or earlier
4. Parser processes negative object number and performs out-of-bounds array write

How to detect it

Monitor process crash logs and core dumps for Xpdf when handling PDF files; review file-access logs for suspicious PDFs delivered shortly before crashes.

What your security team should do

• Prioritize upgrade of all Xpdf installations to a patched release
• Restrict opening of untrusted PDF files on systems running Xpdf
• Implement application allow-listing to limit use of legacy PDF viewers