Answer in brief
CVE-2026-86205 records a Medium severity (CVSS 5.4) vulnerability in h3 before 2.0.1-rc.18 Open Redirect via redirectBack(). The current sources do not mark it as known exploited. The current feed maps h3js/h3 (generic), h3 (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.4. 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.
The current feed maps h3js/h3 (generic), h3 (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| h3js/h3generic | >=2.0.1-rc.17 <2.0.1-rc.18 | 2.0.1-rc.18 |
| h3npm | >=2.0.1-rc.17 <2.0.1-rc.18 | 2.0.1-rc.18 |
Published upstream
Sep 6, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 6, 2026
h3 versions before 2.0.1-rc.18 contain an open redirect vulnerability in the redirectBack() utility that fails to sanitize protocol-relative paths in the Referer header pathname. Attackers can craft a same-origin URL with a double-slash path segment that passes origin validation but produces a Location header interpreted by browsers as a protocol-relative redirect to an external domain.
Quoted source text, attributed separately from HOL analysis.