CVE-2026-27026

low-risk

Published 2026-02-20

pypdf is a free and open-source pure-python PDF library. Prior to 6.7.1, an attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.

Do I need to act?

0.01% chance of exploitation

EPSS score — low exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 5.5/10 Medium

LOCAL / LOW complexity

Affected Products (1)

Pypdf

Affected Vendors

Pypdf Project

References (4)

Patch https://github.com/py-pdf/pypdf/commit/7905842d833f899f1d3228af7e7467ad80277016

Issue Tracking https://github.com/py-pdf/pypdf/pull/3644

Product https://github.com/py-pdf/pypdf/releases/tag/6.7.1

Patch https://github.com/py-pdf/pypdf/security/advisories/GHSA-9mvc-8737-8j8h

/ 100

low-risk

Severity 18/34 · Moderate

Exploitability 0/34 · Minimal

Exposure 5/34 · Minimal