CVE-2026-113786: Input Validation Flaw

Description

pypdf is a free and open-source pure-python PDF library. Prior to 6.21.1, an attacker can craft a PDF containing image data labeled with the /DCTDecode filter that causes Pillow to select and invoke an unintended image parser when the image is loaded. Environments without the optional Pillow dependency are not affected. This issue is fixed in version 6.21.1.

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Weakness Type (CWE)

CWE-20 Improper Input Validation

CWE-183 CWE-183

References

Other References

https://github.com/py-pdf/pypdf/commit/512d8eb94eb04be1d1c90504e6da2dcef8679e07 https://github.com/py-pdf/pypdf/pull/4222 https://github.com/py-pdf/pypdf/releases/tag/6.21.1 https://github.com/py-pdf/pypdf/security/advisories/GHSA-5hx5-vpf9-5wcv

Frequently Asked Questions

What is CVE-2026-113786? +

pypdf is a free and open-source pure-python PDF library. Prior to 6.21.1, an attacker can craft a PDF containing image data labeled with the /DCTDecode filter that causes Pillow to select and invoke an unintended image parser when the image is loaded. Environments without the optional Pillow dependency are not affected. This issue is fixed in version 6.21.1.

How do I check if I'm vulnerable to CVE-2026-113786? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-113786