CVE-2026-77220

Received Received - Intake

Dangling Pointer in PDFio Library

Publication date: 2026-08-21

Last updated on: 2026-08-21

Assigner: VulnCheck

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.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-21

Last Modified

2026-08-21

Generated

2026-08-22

AI Q&A

2026-08-22

EPSS Evaluated

N/A

NVD

CVE-2026-77220

Affected Vendors & Products

Vendor	Product	Version / Range
pdfio	pdfio	to 1.6.5 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-825	The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.

Attack-Flow Graph

Executive Summary

PDFio before 1.6.5 has a dangling pointer issue in its dictionary string-formatting function. It stores a pointer to a stack-local buffer in the document dictionary without copying the string value. In multi-threaded or pooled-request environments, this can lead to stack memory reuse across requests, causing one user's document data to overwrite another's.

Detection Guidance

This vulnerability is specific to PDFio library versions before 1.6.5 and involves dangling pointers in dictionary string formatting. Detection requires checking installed PDFio versions and analyzing multi-threaded PDF processing environments for memory corruption symptoms.

Impact Analysis

This vulnerability can cause document content corruption in multi-threaded or pooled environments. Attackers or concurrent users may exploit it to overwrite one user's document data with another's, leading to data leaks, incorrect document rendering, or potential unauthorized access to sensitive information.

Compliance Impact

This vulnerability could lead to data breaches or unauthorized data exposure, violating GDPR's integrity and confidentiality principles and HIPAA's safeguards for protected health information. Compliance may be compromised if sensitive data is corrupted or leaked due to the flaw.

Mitigation Strategies

Update PDFio to version 1.6.5 or later to address the dangling pointer vulnerability. Avoid multi-threaded or pooled-request environments until patched. Monitor for document corruption or unexpected behavior in PDF processing.

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