CVE-2026-86205
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.
Scoring
- Severity
- MEDIUM
- CVSS base score
- 5.4
- CVSS vector
- 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
- EPSS probability
- 0.20%
- CWE
- CWE-601
- Published
- 2026-09-06
- Last modified
- 2026-09-08
Affected products
- h3js h3
- h3js h3
Weakness type
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