PYSEC-2026-1832

Vulnerability from pysec - Published: 2026-07-07 16:03 - Updated: 2026-07-07 17:25
VLAI
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
Impacted products
Name purl
pypdf pkg:pypi/pypdf
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "pypdf",
        "purl": "pkg:pypi/pypdf"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.0",
        "1.1",
        "1.10",
        "1.11",
        "1.12",
        "1.13",
        "1.2",
        "1.3",
        "1.4",
        "1.5",
        "1.6",
        "1.7",
        "1.8",
        "1.9",
        "3.1.0",
        "3.10.0",
        "3.11.0",
        "3.11.1",
        "3.12.0",
        "3.12.1",
        "3.12.2",
        "3.13.0",
        "3.14.0",
        "3.15.0",
        "3.15.1",
        "3.15.2",
        "3.15.3",
        "3.15.4",
        "3.15.5",
        "3.16.0",
        "3.16.1",
        "3.16.2",
        "3.16.3",
        "3.16.4",
        "3.17.0",
        "3.17.1",
        "3.17.2",
        "3.17.3",
        "3.17.4",
        "3.2.0",
        "3.2.1",
        "3.3.0",
        "3.4.0",
        "3.4.1",
        "3.5.0",
        "3.5.1",
        "3.5.2",
        "3.6.0",
        "3.7.0",
        "3.7.1",
        "3.8.0",
        "3.8.1",
        "3.9.0",
        "3.9.1",
        "4.0.0",
        "4.0.1",
        "4.0.2",
        "4.1.0",
        "4.2.0",
        "4.3.0",
        "4.3.1",
        "5.0.0",
        "5.0.1",
        "5.1.0",
        "5.2.0",
        "5.3.0",
        "5.3.1",
        "5.4.0",
        "5.5.0",
        "5.6.0",
        "5.6.1",
        "5.7.0",
        "5.8.0",
        "5.9.0",
        "6.0.0",
        "6.1.0",
        "6.1.1",
        "6.1.2",
        "6.1.3",
        "6.2.0",
        "6.3.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2025-66019",
    "GHSA-m449-cwjh-6pw7"
  ],
  "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": "PYSEC-2026-1832",
  "modified": "2026-07-07T17:25:13.028239Z",
  "published": "2026-07-07T16:03:10.809096Z",
  "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"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/pypdf"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-m449-cwjh-6pw7"
    }
  ],
  "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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