Medium severity · published Nov 25, 2025
CVE-2025-66019
pypdf manipulated LZWDecode streams can exhaust RAM
6.6
CVSS
0.4%
EPSS
No
On KEV
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 33% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
pypdf · py-pdf
< 6.4.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-66019
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-66019
github.com
https://github.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2
github.com
https://github.com/py-pdf/pypdf/releases/tag/6.4.0
github.com
https://github.com/py-pdf/pypdf/security/advisories/GHSA-m449-cwjh-6pw7
aydinnyunus.github.io
https://aydinnyunus.github.io/2025/12/20/cve-2025-66019-pypdf-lzw-dos/
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