CVE-2025-66019

Description

### 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](https://github.com/py-pdf/pypdf/security/advisories/GHSA-jfx9-29x2-rv3j) to align the default limit with the one for *zlib*. ### Patches This has been fixed in [pypdf==6.4.0](https://github.com/py-pdf/pypdf/releases/tag/6.4.0). ### Workarounds If users cannot upgrade yet, use the line below to overwrite the default in their code: ```python pypdf.filters.LZW_MAX_OUTPUT_LENGTH = 75_000_000 ```

How to fix CVE-2025-66019

To remediate CVE-2025-66019, upgrade the affected package to a fixed version below.

• —upgrade to 6.4.0 or later

Is CVE-2025-66019 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (1)

• from 0, < 6.4.0

CVSS scores

References (7)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2025-66019
• PATCHgithub.com/py-pdf/pypdf
• WEBaydinnyunus.github.io/2025/12/20/cve-2025-66019-pypdf-lzw-dos
• WEBgithub.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2
• WEB