CVE-2026-86205
h3 before 2.0.1-rc.18 Open Redirect via redirectBack()
- State
- Published
- Severity
- 5.3 Medium
- Published
- Sep 6, 2026
- Updated
- Sep 8, 2026
- Reserved
- Sep 5, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 5.3 Medium | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 5.4 Medium | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N | VulnCheck |
Weaknesses
- CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
Affected Products
| Product | Versions |
|---|---|
h3h3js |
|
References
- GitHub Security Advisory (GHSA-fp4x-ggrf-wmc6)vendor-advisory
- VulnCheck Advisory: h3 before 2.0.1-rc.18 Open Redirect via redirectBack()third-party-advisory
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