What’s Vulnerable › Vulnerabilities

CVE-2026-82398: pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace

• Severity: medium (CVSS 5.3 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: 2026-08-31 · updated 2026-10-05
• Weakness: CWE-407

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.15.0, an attacker can craft a PDF that causes long runtimes when the pypdf/_utils.py function read_until_whitespace reads a stream containing a long run of bytes without whitespace. The function repeatedly performs immutable bytes concatenation in a one-byte loop, causing quadratic processing cost for the long non-whitespace input. This issue is fixed in version 6.15.0.

Affected products

• py-pdf pypdf: before 6.15.0 — fixed in 6.15.0

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.15.0. Check the vendor advisory for mitigations.

References

• https://github.com/py-pdf/pypdf/commit/4959848e057e37c218dccad7465259210923faaa
• https://github.com/py-pdf/pypdf/pull/3947
• https://github.com/py-pdf/pypdf/releases/tag/6.15.0
• https://github.com/py-pdf/pypdf/security/advisories/GHSA-fc8x-2rww-xw9m

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