{"id":"CVE-2026-86205","title":"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","summary":"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 …","severity":"medium","cvss":5.4,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N","cwe":["CWE-601"],"vendor":"h3js","product":"h3","affected":["h3 >= 2.0.1-rc.17 < 2.0.1-rc.18"],"published":"2026-09-06","updated":"2026-09-08","sourceUpdated":"2026-09-08T20:00:18.870","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-86205","references":[{"url":"https://github.com/h3js/h3/security/advisories/GHSA-fp4x-ggrf-wmc6","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-open-redirect-via-redirectback","label":"disclosure@vulncheck.com"},{"url":"https://github.com/h3js/h3/security/advisories/GHSA-fp4x-ggrf-wmc6","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86205.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-86205"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2529167"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-86205"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86205"}],"tags":["nvd","cve.org","exploit-available","csaf","vex","red-hat"],"epss":0.00197,"epssPercentile":0.09772,"exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"no","technicalImpact":"partial","timestamp":"2026-09-08T13:28:03.688110Z"},"ingestedAt":"2026-09-07T03:04:07.439Z","slug":"CVE-2026-86205","body":"## Overview\n\nh3 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat OpenShift AI (RHOAI) · no fix planned: Red Hat OpenShift AI (RHOAI) · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86205.json)","depth":"twilight","depthScore":42,"depthScoreParts":{"impact":29.7,"likelihood":0,"exploitation":12,"ransomware":0},"changes":[{"seq":5515,"id":"CVE-2026-86205","ts":1788887297240,"field":"exploit_available","old":"false","new":"true"},{"seq":4391,"id":"CVE-2026-86205","ts":1788886404514,"field":"exploit_available","old":"true","new":"false"},{"seq":3104,"id":"CVE-2026-86205","ts":1788883068406,"field":"exploit_available","old":"false","new":"true"},{"seq":2133,"id":"CVE-2026-86205","ts":1788882472390,"field":"exploit_available","old":"true","new":"false"},{"seq":296,"id":"CVE-2026-86205","ts":1788881646373,"field":"exploit_available","old":"false","new":"true"}]}