What’s Vulnerable › Vulnerabilities

CVE-2025-55197: pypdf's Manipulated FlateDecode streams can exhaust RAM

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-08-13 · updated 2026-06-17
• Weakness: CWE-400

Description

pypdf is a free and open-source pure-python PDF library. Prior to version 6.0.0, an attacker 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. This issue has been fixed in 6.0.0. If an update is not possible, a workaround involves including the fixed code from pypdf.filters.decompress into the existing filters file.

Affected products

• py-pdf pypdf: before 6.0.0 — fixed in 6.0.0

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.0.0. Check the vendor advisory for mitigations.

References

• https://github.com/py-pdf/pypdf/blob/0dd57738bbdcdb63f0fb43d8a6b3d222b6946595/pypdf/filters.py#L72-L143
• https://github.com/py-pdf/pypdf/issues/3429
• https://github.com/py-pdf/pypdf/pull/3430
• https://github.com/py-pdf/pypdf/releases/tag/6.0.0
• https://github.com/py-pdf/pypdf/security/advisories/GHSA-7hfw-26vp-jp8m

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