{"id":"CVE-2026-23527","aliases":["CLSA-2026-1790616002","EUVD-2026-2737","GHSA-mp2g-9vg9-f4cg"],"status":"published","title":"h3 v1 has Request Smuggling (TE.TE) issue","description":"H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.","severity":{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00626,"percentile":0.50474,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-444"],"published":"2026-01-15T19:24:20Z","modified":"2026-10-28T02:31:09Z","fixes":[{"ecosystem":"npm","package":"h3","fixed_in":["1.15.5"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"h3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"1.15.4"},{"fixed":"1.15.5"}]}]},{"source":"osv","ecosystem":"TuxCare:npm","package":"h3","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"1.15.3-tuxcare.0"},{"fixed":"1.15.3-tuxcare.1"}]}],"versions":["1.15.3"],"bundled":2},{"source":"osv","ecosystem":"npm","package":"h3","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.15.5"}]}]}],"products":[{"vendor":"h3","product":"h3"},{"vendor":"h3js","product":"h3"}],"references":[{"url":"https://github.com/h3js/h3/security/advisories/GHSA-mp2g-9vg9-f4cg","tags":["x_refsource_CONFIRM","Exploit","Vendor Advisory","advisory","web"]},{"url":"https://github.com/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097","tags":["x_refsource_MISC","Patch","fix","web"]},{"url":"https://github.com/h3js/h3/releases/tag/v1.15.5","tags":["x_refsource_MISC","web"]},{"url":"https://simonkoeck.com/writeups/h3-transfer-encoding-request-smuggling","tags":["x_refsource_MISC","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-23527","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-mp2g-9vg9-f4cg"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/23xxx/CVE-2026-23527.json","tags":["advisory"]},{"url":"https://github.com/h3js/h3","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-23527","title":"h3 v1 has Request Smuggling (TE.TE) issue","description":"H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.","status":"published","published":"2026-01-15T19:24:20.514Z","modified":"2026-04-13T16:48:19.873Z","cvss":[{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high","assessor":"cna"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T13:42:15.603999Z"}],"euvd":[{"id":"EUVD-2026-2737","description":"H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.","status":"published","published":"2026-01-15T19:24:20Z","modified":"2026-04-13T16:48:19Z","cvss":[{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high"}],"updated_at":"2026-11-02T19:24:27.467761Z"}],"ghsa":[{"id":"GHSA-mp2g-9vg9-f4cg","title":"h3 v1 has Request Smuggling (TE.TE) issue","description":"I was digging into h3 v1 (specifically v1.15.4) and found a critical HTTP Request Smuggling vulnerability.\n\nBasically, `readRawBody` is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive.\n\n**The Bug**: If I send a request with Transfer-Encoding: ChuNked (mixed case), h3 misses it. Since it doesn't see \"chunked\" and there's no Content-Length, it assumes the body is empty and processes the request immediately.\n\nThis leaves the actual body sitting on the socket, which triggers a classic TE.TE Desync (Request Smuggling) if the app is running behind a Layer 4 proxy or anything that doesn't normalize headers (like AWS NLB or Node proxies).\n\n**Vulnerable Code** (`src/utils/body.ts`):\n\n```js\nif (\n    !Number.parseInt(event.node.req.headers[\"content-length\"] || \"\") \u0026\u0026\n    !String(event.node.req.headers[\"transfer-encoding\"] ?? \"\")\n      .split(\",\")\n      .map((e) =\u003e e.trim())\n      .filter(Boolean)\n      .includes(\"chunked\") // \u003c--- This is the issue. \"ChuNkEd\" returns false here.\n  ) {\n    return Promise.resolve(undefined);\n  }\n```\n\nI verified this locally:\n\n- Sent a `Transfer-Encoding: ChunKed` request without a closing 0 chunk.\n- Express hangs (correctly waiting for data).\n- h3 responds immediately (vulnerable, thinks body is length 0).\n\n**Impact**: Since H3/Nuxt/Nitro is often used in containerized setups behind TCP load balancers, an attacker can use this to smuggle requests past WAFs or desynchronize the socket to poison other users' connections.\n\n**Fix**: Just need to normalize the header value before checking: ` .map((e) =\u003e e.trim().toLowerCase())`","status":"published","published":"2026-01-15T20:10:51Z","modified":"2026-04-13T16:47:53Z","cvss":[{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:39:53.087746Z"}],"nvd":[{"id":"CVE-2026-23527","description":"H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.","status":"published","published":"2026-01-15T20:16:05.62Z","modified":"2026-06-17T10:21:43.847Z","cvss":[{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high","assessor":"secondary"},{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical","assessor":"primary"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:12:04.066712Z"}],"osv":[{"id":"CVE-2026-23527","title":"h3 v1 has Request Smuggling (TE.TE) issue","description":"H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.","status":"published","published":"2026-01-15T19:24:20.514Z","modified":"2026-10-28T02:31:09.401260994Z","cvss":[{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:44:59.079784Z"},{"id":"GHSA-mp2g-9vg9-f4cg","title":"h3 v1 has Request Smuggling (TE.TE) issue","description":"I was digging into h3 v1 (specifically v1.15.4) and found a critical HTTP Request Smuggling vulnerability.\n\nBasically, `readRawBody` is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for \"chunked\", but per the RFC, this header should be case-insensitive.\n\n**The Bug**: If I send a request with Transfer-Encoding: ChuNked (mixed case), h3 misses it. Since it doesn't see \"chunked\" and there's no Content-Length, it assumes the body is empty and processes the request immediately.\n\nThis leaves the actual body sitting on the socket, which triggers a classic TE.TE Desync (Request Smuggling) if the app is running behind a Layer 4 proxy or anything that doesn't normalize headers (like AWS NLB or Node proxies).\n\n**Vulnerable Code** (`src/utils/body.ts`):\n\n```js\nif (\n    !Number.parseInt(event.node.req.headers[\"content-length\"] || \"\") \u0026\u0026\n    !String(event.node.req.headers[\"transfer-encoding\"] ?? \"\")\n      .split(\",\")\n      .map((e) =\u003e e.trim())\n      .filter(Boolean)\n      .includes(\"chunked\") // \u003c--- This is the issue. \"ChuNkEd\" returns false here.\n  ) {\n    return Promise.resolve(undefined);\n  }\n```\n\nI verified this locally:\n\n- Sent a `Transfer-Encoding: ChunKed` request without a closing 0 chunk.\n- Express hangs (correctly waiting for data).\n- h3 responds immediately (vulnerable, thinks body is length 0).\n\n**Impact**: Since H3/Nuxt/Nitro is often used in containerized setups behind TCP load balancers, an attacker can use this to smuggle requests past WAFs or desynchronize the socket to poison other users' connections.\n\n**Fix**: Just need to normalize the header value before checking: ` .map((e) =\u003e e.trim().toLowerCase())`","status":"published","published":"2026-01-15T20:10:51Z","modified":"2026-04-13T17:15:15.108956Z","cvss":[{"version":"3.1","score":8.9,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L","level":"high"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:46:52.170928Z"},{"id":"CLSA-2026-1790616002","title":"TuxCare security update for h3 (2 CVEs)","description":"TuxCare rebuilt h3 to address 2 CVEs. Fixed in 1.15.3-tuxcare.1.","status":"published","published":"2026-09-28T17:20:02Z","modified":"2026-10-15T09:48:03.991587108Z","updated_at":"2026-11-02T15:43:48.65893Z"}]}}