What is CVE-2026-27026?

CVE-2026-27026 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.5/10. Published 2026-02-20.

How severe is CVE-2026-27026?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Resource exhaustion in Py-Pdf Pypdf

CVE-2026-27026

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.

Published 2026-02-20 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.002 (7.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 7th percentile — 7.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Py-Pdf Pypdf — versions < 6.7.1
Pypdf Project

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

github.com/py-pdf/pypdf/security/advisories/GHSA-9mvc-8737-8j8h (Patch, Vendor Advisory)
github.com/py-pdf/pypdf/pull/3644 (Patch, Issue Tracking)
github.com/py-pdf/pypdf/commit/7905842d833f899f1d3228af7e7467ad80277016 (Patch)
github.com/py-pdf/pypdf/releases/tag/6.7.1 (Product, Release Notes)

Frequently asked questions

What is CVE-2026-27026?: CVE-2026-27026 is a medium-severity vulnerability in Py-Pdf Pypdf, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.5/10. Published 2026-02-20.
How severe is CVE-2026-27026?: Medium severity. CVSS v3 base score is 5.5 out of 10.