{"id":"CVE-2026-86252","title":"h3 versions before 1.15.9 fail to sanitize carriage return characters in EventStream data and comment fields, allowing attackers to inject arbitrary SSE events by including unsanitized carriage returns","summary":"h3 versions before 1.15.9 fail to sanitize carriage return characters in EventStream data and comment fields, allowing attackers to inject arbitrary SSE events by including unsanitized carriage returns. Attackers can inject event type di…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cwe":["CWE-74","CWE-93"],"vendor":"h3js","product":"h3","affected":["h3 < 1.15.9","h3 >= 2.0.0-beta.0 < 2.0.1-rc.17"],"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-2026-86252","references":[{"url":"https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/h3-before-1.15.9-sse-event-injection-via-carriage-return","label":"disclosure@vulncheck.com"},{"url":"https://github.com/h3js/h3/security/advisories/GHSA-4hxc-9384-m385","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-86252.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-86252"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2529158"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-86252"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86252"}],"tags":["nvd","cve.org","exploit-available","csaf","vex","red-hat"],"epss":0.00216,"epssPercentile":0.12222,"exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-08T15:11:57.605320Z"},"ingestedAt":"2026-09-07T04:04:50.585Z","slug":"CVE-2026-86252","body":"## Overview\n\nh3 versions before 1.15.9 fail to sanitize carriage return characters in EventStream data and comment fields, allowing attackers to inject arbitrary SSE events by including unsanitized carriage returns. Attackers can inject event type directives, split single push calls into multiple browser-parsed events, or escape comment fields to inject data, bypassing the prior CVE fix that only addressed newline injection.\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-2026-86252.json)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":12,"ransomware":0},"changes":[{"seq":5535,"id":"CVE-2026-86252","ts":1788887297454,"field":"exploit_available","old":"false","new":"true"},{"seq":4410,"id":"CVE-2026-86252","ts":1788886404730,"field":"exploit_available","old":"true","new":"false"},{"seq":3123,"id":"CVE-2026-86252","ts":1788883068609,"field":"exploit_available","old":"false","new":"true"},{"seq":2152,"id":"CVE-2026-86252","ts":1788882472602,"field":"exploit_available","old":"true","new":"false"},{"seq":310,"id":"CVE-2026-86252","ts":1788881649230,"field":"exploit_available","old":"false","new":"true"}]}