CVE-2026-27025: pypdf has possible long runtimes/large memory usage for large /ToUnicode streams

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-20 · updated 2026-06-17
Weakness: CWE-834

Description

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 and large memory consumption. This requires parsing the /ToUnicode entry of a font with unusually large values, for example during text extraction. This vulnerability is fixed in 6.7.1.

Affected products

py-pdf pypdf: before 6.7.1 — fixed in 6.7.1

How to fix

Upgrade to a fixed version: py-pdf pypdf 6.7.1. Check the vendor advisory for mitigations.

References

https://github.com/py-pdf/pypdf/commit/77d7b8d7cfbe8dd179858dfa42666f73fc6e57a2
https://github.com/py-pdf/pypdf/pull/3646
https://github.com/py-pdf/pypdf/releases/tag/6.7.1
https://github.com/py-pdf/pypdf/security/advisories/GHSA-wgvp-vg3v-2xq3

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