---
id: CVE-2026-28804
aliases:
  - GHSA-9m86-7pmv-2852
  - PYSEC-2026-3014
title: pypdf vulnerable to inefficient decoding of ASCIIHexDecode streams
summary: pypdf vulnerable to inefficient decoding of ASCIIHexDecode streams
severity: medium
vendor: pypdf
product: pypdf
ecosystem: pip
affected:
  - pypdf < 6.7.5
patched:
  - pypdf 6.7.5
published: '2026-03-02'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:50:38.603469156Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-9m86-7pmv-2852'
references:
  - url: 'https://github.com/py-pdf/pypdf/security/advisories/GHSA-9m86-7pmv-2852'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-28804'
  - url: 'https://github.com/py-pdf/pypdf/pull/3666'
  - url: >-
      https://github.com/py-pdf/pypdf/commit/648c627d2657447dfb1773412af05a0a5103b98f
  - url: 'https://github.com/py-pdf/pypdf'
  - url: 'https://github.com/py-pdf/pypdf/releases/tag/6.7.5'
tags:
  - osv
  - pip
epss: 0.00399
epssPercentile: 0.33952
ingestedAt: '2026-07-13T18:57:56.000Z'
---

## Overview

### Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires accessing a stream which uses the `/ASCIIHexDecode` filter.

### Patches
This has been fixed in [pypdf==6.7.5](https://github.com/py-pdf/pypdf/releases/tag/6.7.5).

### Workarounds
If you cannot upgrade yet, consider applying the changes from PR [#3666](https://github.com/py-pdf/pypdf/pull/3666).

## Affected packages

- `pypdf < 6.7.5`

## Remediation

Upgrade to a patched release:

- `pypdf 6.7.5`