Vulnerability · Published Nov 25, 2025 · Assigned by GitHub_M

CVE-2025-66019pypdf manipulated LZWDecode streams can exhaust RAM

Medium 6.6

In plain English

A medium-severity uncontrolled resource consumption in pypdf from py-pdf. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 33% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.6Medium

Exploit odds (30 days)0.4%top 67.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	pypdf	6.4.0	GHSA-m449-cwjh-6pw7
PyPI	pypdf	6.4.0	PYSEC-2026-1832
Ubuntu:24.04:LTS	pypdf	no fix listed	UBUNTU-CVE-2025-66019
Ubuntu:25.10	pypdf	no fix listed	UBUNTU-CVE-2025-66019
Ubuntu:26.04:LTS	pypdf	no fix listed	UBUNTU-CVE-2025-66019
Ubuntu:26.10	pypdf	no fix listed	UBUNTU-CVE-2025-66019

Affected products (as reported)

Vendor	Product	Versions
py-pdf	pypdf	< 6.4.0

Weakness: CWE-400, CWE-409 · 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

References

https://github.com/py-pdf/pypdf/security/advisories/GHSA-m449-cwjh-6pw7 x_refsource_CONFIRM
https://github.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2 x_refsource_MISC
https://github.com/py-pdf/pypdf/releases/tag/6.4.0 x_refsource_MISC
https://aydinnyunus.github.io/2025/12/20/cve-2025-66019-pypdf-lzw-dos/