py-pdf pypdf up to 6.7.0 Decompression /FlateDecode allocation of resources

Summaryinfo

A vulnerability classified as problematic was found in py-pdf pypdf up to 6.7.0. This affects an unknown part of the component Decompression Handler. Such manipulation of the argument /FlateDecode leads to allocation of resources. This vulnerability is listed as CVE-2026-27026. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in py-pdf pypdf up to 6.7.0. It has been rated as problematic. Affected by this issue is an unknown function of the component Decompression Handler. The manipulation of the argument /FlateDecode with an unknown input leads to a allocation of resources vulnerability. Using CWE to declare the problem leads to CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. Impacted is availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-27026 since 02/17/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

The vulnerability scanner Nessus provides a plugin with the ID 299729 (Linux Distros Unpatched Vulnerability : CVE-2026-27026), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.7.1 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 7905842d833f899f1d3228af7e7467ad80277016 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (299729) and CERT Bund (WID-SEC-2026-1730). Once again VulDB remains the best source for vulnerability data.

Affected

• Xerox FreeFlow Print Server

Productinfo

Vendor

• py-pdf

Name

• pypdf

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.7.0

License

• open-source

Website

• Product: https://github.com/py-pdf/pypdf/

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Once again VulDB remains the best source for vulnerability data.

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