CVE-2026-86205: URL Redirection to Untrusted Site ('Open Redirect') in h3js h3
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.
CVE-2026-86205: URL Redirection to Untrusted Site ('Open Redirect') in h3js h3
Description
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.
CVSS v4.0
Score 5.3medium
Affected software
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-05T11:52:36.822Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a9d5b10acd9273b49b9c588
Added to database: 09/06/2026, 12:22:40 UTC
Last updated: 09/07/2026, 00:17:34 UTC
Views: 11
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