CVE-2026-77220

Medium

Description

PDFio before 1.6.5 contains a dangling pointer vulnerability in the dictionary string-formatting function that stores a pointer to a stack-local buffer in the document dictionary without copying the string value. In multi-threaded or pooled-request environments, attackers or concurrent users can trigger stack memory reuse across requests, causing cross-tenant document content corruption by silently overwriting one caller's dictionary string values with another caller's data.

SeverityMedium

CVSS6.5

Exploit probability—

ProductMichaelrsweet Pdfio

PublishedAug 21, 2026

First seenAug 21, 2026

Weakness typeCWE-825CWE-825

How to fix

Update

michaelrsweet pdfio1.6.5 or later

Patches

github.com/michaelrsweet/pdfio/commit/22b9afc800c5833f9e851e35938972bd4c76a357

Vendor advisories

github.com/michaelrsweet/pdfio/releases/tag/v1.6.5

Affected products

Product	Affected versions	Fixed in
michaelrsweet pdfio	v < 1.6.5	1.6.5

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