PDFio < 1.6.5 Dangling Pointer via Dictionary String-Formatting (CVE-2026-77220) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-77220

PDFio < 1.6.5 Dangling Pointer via Dictionary String-Formatting

Answer in brief

CVE-2026-77220 records a Unknown severity vulnerability in PDFio < 1.6.5 Dangling Pointer via Dictionary String-Formatting. The current sources do not mark it as known exploited. The current feed maps michaelrsweet/pdfio (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 21, 2026Updated Aug 21, 2026Source checked Aug 21, 2026First seen by HOL Aug 21, 2026Material review Aug 21, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps michaelrsweet/pdfio (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
michaelrsweet/pdfiogeneric	>=0 <1.6.5	1.6.5

Recommended response

Check inventory. Check lockfiles and deployed manifests for michaelrsweet/pdfio.
Review the reported fix. Update michaelrsweet/pdfio to 1.6.5 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 21, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 21, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.