---
id: GHSA-6fj4-rcr3-r7rr
title: lopdf has a stack overflow via deeply nested PDF objects
summary: lopdf has a stack overflow via deeply nested PDF objects
severity: high
cvss: 7.5
cwe:
  - CWE-1124
vendor: lopdf
product: lopdf
ecosystem: rust
affected:
  - lopdf < 0.42.0
patched:
  - lopdf 0.42.0
published: '2026-10-16'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T19:55:40Z'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-6fj4-rcr3-r7rr'
references:
  - url: 'https://github.com/J-F-Liu/lopdf/issues/502'
  - url: 'https://github.com/J-F-Liu/lopdf/pull/503'
  - url: >-
      https://github.com/J-F-Liu/lopdf/commit/c755394ad7dd651ccfe77c618f90ab779da1dfd9
  - url: 'https://rustsec.org/advisories/RUSTSEC-2026-0187.html'
  - url: 'https://github.com/advisories/GHSA-6fj4-rcr3-r7rr'
tags:
  - ghsa
  - rust
ingestedAt: '2026-10-16T20:51:39.884Z'
---

## Overview

`lopdf::Document::load_mem` (and the other `load*` entry points) parses nested PDF arrays and dictionaries with unbounded recursion. A small crafted PDF whose Catalog contains a deeply nested array (`/X [[[ … ]]]`, on the order of 10,000 levels) exhausts the call stack and aborts the process with `SIGABRT`.

Because this is a stack-overflow abort rather than a `panic!`, it cannot be caught with `catch_unwind`: any service that parses untrusted PDF input with lopdf can be crashed by a ~21 KB file, resulting in a denial of service.

Confirmed on lopdf 0.41.0 and earlier; fixed in 0.42.0. Default configuration, no features changed.

## Proof of concept

```rust
fn main() {
    let bytes = std::fs::read("poc.pdf").unwrap(); // ~10,380-deep nested array in the Catalog
    let _ = lopdf::Document::load_mem(&bytes);     // stack overflow -> SIGABRT
}
```

An equivalent PoC is a minimal PDF whose Catalog `/X` value is `"[" * 10380 + "]" * 10380`.

## Suggested fix

Enforce a maximum object-nesting depth in the parser and return an `Err` instead of recursing without bound.

## Affected packages

- `lopdf < 0.42.0`

## Remediation

Upgrade to a patched release:

- `lopdf 0.42.0`