CVE-2026-77220

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.

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