---
id: CVE-2026-102997
title: pypdf is a free and open-source pure-python PDF library
summary: >-
  pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a
  crafted PDF containing a partially malformed /FlateDecode stream with padded
  data can force pypdf/filters.py to use inefficient byte-by-byte decompression
  while …
severity: high
cvss: 8.7
cvssVector: 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'
cwe:
  - CWE-400
  - CWE-407
vendor: py-pdf
product: pypdf
affected:
  - pypdf < 6.18.1
published: '2026-09-30'
updated: '2026-09-30'
sourceUpdated: '2026-09-30T21:17:07.020'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102997'
references:
  - url: >-
      https://github.com/py-pdf/pypdf/commit/d9d38cf99b115deb562d3b68f36c33027bc04f79
    label: security-advisories@github.com
  - url: 'https://github.com/py-pdf/pypdf/pull/4073'
    label: security-advisories@github.com
  - url: 'https://github.com/py-pdf/pypdf/releases/tag/6.18.1'
    label: security-advisories@github.com
  - url: 'https://github.com/py-pdf/pypdf/security/advisories/GHSA-jw7q-gvrg-4vj3'
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
cvssSource: cna
ingestedAt: '2026-09-30T21:25:07.839Z'
---

## Overview

pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filters.py to use inefficient byte-by-byte decompression while the earlier recovery counter fails to advance for bytes that successfully decode, causing long runtimes and application unavailability. This is a residual issue after the malformed FlateDecode recovery fix. This issue is fixed in version 6.18.1.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.