Corrupt PDF with a broken xref table

Handle it in code

Each snippet below was run against this exact file with Python 3.14.4 and Node 24.15.0 when this page was built, and the output shown is what it printed.

Python

A cheap structural check before handing the file to a PDF library, which will often repair these silently. Use it to reject or flag uploads, not to validate PDFs fully.

import re

with open("corrupt-xref.pdf", "rb") as f:
    data = f.read()

problems = []
if not data.startswith(b"%PDF-"):
    problems.append("no %PDF- header")
tail = data[-1024:]
if b"%%EOF" not in tail:
    problems.append("no %%EOF marker: the file is truncated")
m = re.search(rb"startxref\s+(\d+)\s+%%EOF", tail)
if m:
    offset = int(m.group(1))
    at = data[offset:offset + 20]
    if offset >= len(data) or not (at.startswith(b"xref") or re.match(rb"\d+ \d+ obj", at)):
        problems.append(f"startxref points at byte {offset}, where there is no cross-reference table")

print("; ".join(problems) or "structure looks intact")

Run against this file, it prints: startxref points at byte 999999, where there is no cross-reference table