{"id":"CVE-2020-5207","aliases":["EUVD-2020-0284","GHSA-xrr9-rh8p-433v"],"status":"published","title":"Request smuggling is possible in Ktor when both chunked TE and content length specified","description":"In Ktor before 1.3.0, request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle \\n as a headers separator.","severity":{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00762,"percentile":0.55633,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-444"],"published":"2020-01-27T19:28:40Z","modified":"2026-10-20T10:54:21Z","fixes":[{"ecosystem":"Maven","package":"io.ktor:ktor-client-cio","fixed_in":["1.3.0"],"sources":["ghsa","osv"]},{"ecosystem":"Maven","package":"io.ktor:ktor-server-cio","fixed_in":["1.3.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Maven","package":"io.ktor:ktor-client-cio","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.0"}]}]},{"source":"ghsa","ecosystem":"Maven","package":"io.ktor:ktor-server-cio","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.0"}]}]},{"source":"osv","ecosystem":"Maven","package":"io.ktor:ktor-client-cio","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.0"}]}],"versions":["1.0.0","1.0.0-rc","1.0.1","1.1.0","1.1.1","1.1.2","1.1.3","1.1.4","1.1.5","1.2.0","1.2.0-rc","1.2.0-rc2","1.2.1","1.2.2","1.2.3","1.2.3-rc","1.2.4","1.2.5","1.2.6","1.3.0-rc","1.3.0-rc2"]},{"source":"osv","ecosystem":"Maven","package":"io.ktor:ktor-server-cio","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.0"}]}],"versions":["1.0.0","1.0.0-rc","1.0.1","1.1.0","1.1.1","1.1.2","1.1.3","1.1.4","1.2.0","1.2.0-rc","1.2.0-rc2","1.2.1","1.2.2","1.2.3","1.2.3-rc","1.2.4","1.2.5","1.2.6","1.3.0-rc","1.3.0-rc2"]}],"products":[{"vendor":"jetbrains","product":"ktor"},{"vendor":"ktor.io","product":"ktor"}],"references":[{"url":"https://github.com/ktorio/ktor/security/advisories/GHSA-xrr9-rh8p-433v","tags":["x_refsource_CONFIRM","x_transferred","Third Party Advisory","advisory","web"]},{"url":"https://github.com/ktorio/ktor/pull/1547","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-5207","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-xrr9-rh8p-433v"}],"sources":{"cve":[{"id":"CVE-2020-5207","title":"Request smuggling is possible in Ktor when both chunked TE and content length specified","description":"In Ktor before 1.3.0, request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle \\n as a headers separator.","status":"published","published":"2020-01-27T19:30:15Z","modified":"2024-08-04T08:22:09.258Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"cna"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:35:47.56691Z"}],"euvd":[{"id":"EUVD-2020-0284","description":"In Ktor before 1.3.0, request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle \\n as a headers separator.","status":"published","published":"2020-01-27T19:30:15Z","modified":"2024-08-04T08:22:09Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-03T03:08:07.28588Z"}],"ghsa":[{"id":"GHSA-xrr9-rh8p-433v","title":"Request smuggling is possible when both chunked TE and content length specified","description":"### Impact\nRequest smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle alone \\n as a headers separator.\n\n### Patches\nhttps://github.com/ktorio/ktor/pull/1547\n\n### Workarounds\nNone except migrating to a better proxy.\n\n### References\nhttps://portswigger.net/web-security/request-smuggling\nhttps://tools.ietf.org/html/rfc7230#section-9.5","status":"published","published":"2020-01-27T19:28:40Z","modified":"2023-01-09T05:02:08Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:36:03.040255Z"}],"nvd":[{"id":"CVE-2020-5207","description":"In Ktor before 1.3.0, request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle \\n as a headers separator.","status":"published","published":"2020-01-27T20:15:10.98Z","modified":"2026-06-17T03:21:01.517Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"primary"},{"version":"2.0","score":5,"vector":"AV:N/AC:L/Au:N/C:N/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:05:53.837808Z"}],"osv":[{"id":"CVE-2020-5207","description":"In Ktor before 1.3.0, request smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle \\n as a headers separator.","status":"published","published":"2020-01-27T20:15:10.98Z","modified":"2026-10-20T10:54:21.933818276Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:44:16.936975Z"},{"id":"GHSA-xrr9-rh8p-433v","title":"Request smuggling is possible when both chunked TE and content length specified","description":"### Impact\nRequest smuggling is possible when running behind a proxy that doesn't handle Content-Length and Transfer-Encoding properly or doesn't handle alone \\n as a headers separator.\n\n### Patches\nhttps://github.com/ktorio/ktor/pull/1547\n\n### Workarounds\nNone except migrating to a better proxy.\n\n### References\nhttps://portswigger.net/web-security/request-smuggling\nhttps://tools.ietf.org/html/rfc7230#section-9.5","status":"published","published":"2020-01-27T19:28:40Z","modified":"2026-07-08T05:59:54.37362839Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:47:00.198893Z"}]}}