What’s Vulnerable › Vulnerabilities

CVE-2026-77220: PDFio < 1.6.5 Dangling Pointer via Dictionary String-Formatting

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-21 · updated 2026-10-12
• Weakness: CWE-825

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.

Affected products

• michaelrsweet pdfio: before 1.6.5 — fixed in 1.6.5

How to fix

Upgrade to a fixed version: michaelrsweet pdfio 1.6.5. Check the vendor advisory for mitigations.

References

• https://github.com/michaelrsweet/pdfio/commit/22b9afc800c5833f9e851e35938972bd4c76a357
• https://github.com/michaelrsweet/pdfio/releases/tag/v1.6.5
• https://www.vulncheck.com/advisories/pdfio-dangling-pointer-via-dictionary-string-formatting

Get alerted when CVE-2026-77220 or the next vulnerability affects your stack