GHSA-9mvc-8737-8j8h

pypdf possibly has long runtimes for malformed FlateDecode streams

Source: GitHub Advisory Database (reviewed) Moderate CVE-2026-27026

Packages

Ecosystem	Package	Affected	Fixed in
PyPI	pypdf	< 6.7.1	6.7.1

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact 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. ### Patches This has been fixed in [pypdf==6.7.1](https://github.com/py-pdf/pypdf/releases/tag/6.7.1). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#3644](https://github.com/py-pdf/pypdf/pull/3644).

References

External links from the advisory. They lead to third-party sites.

https://github.com/py-pdf/pypdf/security/advisories/GHSA-9mvc-8737-8j8h web
https://nvd.nist.gov/vuln/detail/CVE-2026-27026 advisory
https://github.com/py-pdf/pypdf/pull/3644 web
https://github.com/py-pdf/pypdf/commit/7905842d833f899f1d3228af7e7467ad80277016 web
https://github.com/py-pdf/pypdf package
https://github.com/py-pdf/pypdf/releases/tag/6.7.1 web