PyPDF's Manipulated FlateDecode streams can exhaust RAM
Impact
An attacker who uses this vulnerability can craft a PDF which leads to the RAM being exhausted. This requires just reading the file if a series of FlateDecode filters is used on a malicious cross-reference stream. Other content streams are affected on explicit access.
Patches
This has been fixed in pypdf==6.0.0.
Workarounds
If you cannot upgrade yet, you might want to implement the workaround for pypdf.filters.decompress yourself: https://github.com/py-pdf/pypdf/blob/0dd57738bbdcdb63f0fb43d8a6b3d222b6946595/pypdf/filters.py#L72-L143
References
This issue has been reported in #3429 and fixed in #3430.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pypdf | < 6.0.0 | 6.0.0 |
References
- https://github.com/py-pdf/pypdf/security/advisories/GHSA-7hfw-26vp-jp8m
- https://nvd.nist.gov/vuln/detail/CVE-2025-55197
- https://github.com/py-pdf/pypdf/issues/3429
- https://github.com/py-pdf/pypdf/pull/3430
- https://github.com/py-pdf/pypdf
- https://github.com/py-pdf/pypdf/blob/0dd57738bbdcdb63f0fb43d8a6b3d222b6946595/pypdf/filters.py#L72-L143
- https://github.com/py-pdf/pypdf/releases/tag/6.0.0
- https://pypi.org/project/pypdf
- https://github.com/advisories/GHSA-7hfw-26vp-jp8m
- CVSS 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- Weakness (CWE)
CWE-400, CWE-770- Platform
- Python (PyPI)
- Package
pypdf- Disclosed
- 13.08.2025
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1830 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-7hfw-26vp-jp8m - CC BY 4.0
Vulnerability history: pypdf
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 51
- First → latest
- 06.2023 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 10
- Medium 38
- Low 3
Disclosures per year
- 2023: 2
- 2024: 0
- 2025: 4
- 2026: 45
-
PyPDF's Manipulated FlateDecode streams can exhaust RAM this entry
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.