---
id: CVE-2026-77220
title: >-
  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
summary: >-
  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
  poo…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-825
published: '2026-08-21'
updated: '2026-09-24'
sourceUpdated: '2026-09-24T20:43:32.537'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-77220'
references:
  - url: >-
      https://github.com/michaelrsweet/pdfio/commit/22b9afc800c5833f9e851e35938972bd4c76a357
    label: disclosure@vulncheck.com
  - url: 'https://github.com/michaelrsweet/pdfio/releases/tag/v1.6.5'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/pdfio-dangling-pointer-via-dictionary-string-formatting
    label: disclosure@vulncheck.com
tags:
  - nvd
epss: 0.00421
epssPercentile: 0.3373
ingestedAt: '2026-09-24T20:51:40.218Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.