CVE-2025-66019
EPSS 0.08%pypdf's LZWDecode streams be manipulated to exhaust RAM
Published: 11/24/2025Modified: 2/4/2026
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 ```
Affected packages (1)
- PyPI/pypdffrom 0, < 6.4.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | 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 (7)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2025-66019
- PATCHhttps://github.com/py-pdf/pypdf
- WEBhttps://aydinnyunus.github.io/2025/12/20/cve-2025-66019-pypdf-lzw-dos
- WEBhttps://github.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2
- WEBhttps://github.com/py-pdf/pypdf/releases/tag/6.4.0
- WEBhttps://github.com/py-pdf/pypdf/security/advisories/GHSA-jfx9-29x2-rv3j
- WEBhttps://github.com/py-pdf/pypdf/security/advisories/GHSA-m449-cwjh-6pw7