CVE-2026-86205: medium-severity vulnerability in h3js h3
h3 before 2.0.1-rc.18 Open Redirect via redirectBack()
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 0.3%
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:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Affected products
h3js · h3Related CVEs — h3js h3
In the same product, most dangerous first.
CVE-2026-23527HIGHh3 v1 has Request Smuggling (TE.TE) issueEPSS 0.6%CVE-2026-86253HIGHh3 before 1.15.6 Path Traversal via Percent-Encoded Dot SegmentsEPSS 0.6%CVE-2026-33128HIGHh3 has a Server-Sent Events Injection via Unsanitized Newlines in Event Stream FieldsEPSS 0.6%CVE-2026-86250HIGHh3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked CookieEPSS 0.5%CVE-2026-86251HIGHh3 before 1.15.9 Path Traversal via Double DecodingEPSS 0.4%CVE-2026-33131HIGHh3 has a middleware bypass with one gadgetEPSS 0.4%