pypdf is a free and open-source pure-python PDF library. Prior to version 6.4.0, 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 issue has been patched in version 6.4.0.

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact None

Vulnerable System Integrity Impact None

Vulnerable System Availability Impact High

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact Low

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.0007.

Exploitation none

Automatable yes

Technical Impact partial

Affected Vendors & Products

Vendors Products
Pypdf Project Subscribe
Pypdf Subscribe

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No data.

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Vendors Products
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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-m449-cwjh-6pw7 pypdf's LZWDecode streams be manipulated to exhaust RAM
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://aydinnyunus.github.io/2025/12/20/cve-2025-66019-pypdf-lzw-dos/ cve-icon
https://github.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2 cve-icon cve-icon cve-icon
https://github.com/py-pdf/pypdf/releases/tag/6.4.0 cve-icon cve-icon cve-icon
https://github.com/py-pdf/pypdf/security/advisories/GHSA-m449-cwjh-6pw7 cve-icon cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2025-66019 cve-icon
https://www.cve.org/CVERecord?id=CVE-2025-66019 cve-icon
History

Wed, 21 Jan 2026 04:30:00 +0900

Type Values Removed Values Added
References

Wed, 03 Dec 2025 09:15:00 +0900

Type Values Removed Values Added
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}

threat_severity

Moderate

Thu, 27 Nov 2025 19:00:00 +0900

Type Values Removed Values Added
First Time appeared Pypdf Project
Pypdf Project pypdf
Vendors & Products Pypdf Project
Pypdf Project pypdf

Thu, 27 Nov 2025 02:15:00 +0900

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 26 Nov 2025 08:45:00 +0900

Type Values Removed Values Added
Description pypdf is a free and open-source pure-python PDF library. Prior to version 6.4.0, 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 issue has been patched in version 6.4.0.
Title pypdf manipulated LZWDecode streams can exhaust RAM
Weaknesses CWE-400
CWE-409
References
Metrics cvssV4_0

{'score': 6.6, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-01-20T18:33:02.928Z

Reserved: 2025-11-21T01:08:02.613Z

Link: CVE-2025-66019

cve-icon Vulnrichment

Updated: 2026-01-20T18:33:02.928Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-11-26T00:15:51.263

Modified: 2026-01-20T19:15:49.413

Link: CVE-2025-66019

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-11-25T23:38:12Z

Links: CVE-2025-66019 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-11-27T18:45:24Z

Weaknesses