CVE-2026-27026
MEDIUM5.5EPSS 0.01%pypdf possibly has long runtimes for malformed FlateDecode streams
Published: 2/18/2026Modified: 4/28/2026
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. This requires a malformed /FlateDecode stream, where the byte-by-byte decompression is used. This vulnerability is fixed in 6.7.1.
Affected packages (3)
- Debian/pypdffrom 0
- Debian/pypdf2from 0
- PyPI/pypdffrom 0, < 6.7.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
| osv | CVSS 3.1 | MEDIUM5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
References (7)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-27026
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2026-27026
- PATCHhttps://github.com/py-pdf/pypdf
- WEBhttps://github.com/py-pdf/pypdf/commit/7905842d833f899f1d3228af7e7467ad80277016
- WEBhttps://github.com/py-pdf/pypdf/pull/3644
- WEBhttps://github.com/py-pdf/pypdf/releases/tag/6.7.1
- WEBhttps://github.com/py-pdf/pypdf/security/advisories/GHSA-9mvc-8737-8j8h