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GHSA-M449-CWJH-6PW7

Vulnerability from github – Published: 2025-11-24 22:42 – Updated: 2026-01-21 16:37
VLAI
Summary
pypdf's LZWDecode streams be manipulated to exhaust RAM
Details

Impact

An attacker who uses this vulnerability can craft a PDF which leads to a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter.

This is a follow up to GHSA-jfx9-29x2-rv3j to align the default limit with the one for zlib.

Patches

This has been fixed in pypdf==6.4.0.

Workarounds

If users cannot upgrade yet, use the line below to overwrite the default in their code:

pypdf.filters.LZW_MAX_OUTPUT_LENGTH = 75_000_000
Severity
6.6 (Medium)
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/E:U
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pypdf"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2025-66019"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-400",
      "CWE-409"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2025-11-24T22:42:07Z",
    "nvd_published_at": "2025-11-26T00:15:51Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nAn attacker who uses this vulnerability can craft a PDF which leads to a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter.\n\nThis is a follow up to [GHSA-jfx9-29x2-rv3j](https://github.com/py-pdf/pypdf/security/advisories/GHSA-jfx9-29x2-rv3j) to align the default limit with the one for *zlib*.\n\n### Patches\nThis has been fixed in [pypdf==6.4.0](https://github.com/py-pdf/pypdf/releases/tag/6.4.0).\n\n### Workarounds\nIf users cannot upgrade yet, use the line below to overwrite the default in their code:\n\n```python\npypdf.filters.LZW_MAX_OUTPUT_LENGTH = 75_000_000\n```",
  "id": "GHSA-m449-cwjh-6pw7",
  "modified": "2026-01-21T16:37:13Z",
  "published": "2025-11-24T22:42:07Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/py-pdf/pypdf/security/advisories/GHSA-jfx9-29x2-rv3j"
    },
    {
      "type": "WEB",
      "url": "https://github.com/py-pdf/pypdf/security/advisories/GHSA-m449-cwjh-6pw7"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-66019"
    },
    {
      "type": "WEB",
      "url": "https://github.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2"
    },
    {
      "type": "WEB",
      "url": "https://aydinnyunus.github.io/2025/12/20/cve-2025-66019-pypdf-lzw-dos"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/py-pdf/pypdf"
    },
    {
      "type": "WEB",
      "url": "https://github.com/py-pdf/pypdf/releases/tag/6.4.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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/E:U",
      "type": "CVSS_V4"
    }
  ],
  "summary": "pypdf\u0027s LZWDecode streams be manipulated to exhaust RAM"
}



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