{"id":"CVE-2020-36202","aliases":["EUVD-2022-3538","GHSA-c8rq-crxj-mj9m","RUSTSEC-2020-0093"],"status":"published","title":"Async-h1 request smuggling possible with long unread bodies","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","severity":{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.00825,"percentile":0.57705,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-444","CWE-79"],"published":"2020-12-17T12:00:00Z","modified":"2026-10-24T10:30:51Z","fixes":[{"ecosystem":"crates.io","package":"async-h1","fixed_in":["2.3.0"],"sources":["ghsa"]}],"affected":[{"source":"ghsa","ecosystem":"crates.io","package":"async-h1","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}]},{"source":"osv","ecosystem":"crates.io","package":"async-h1","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}],"bundled":2},{"source":"osv","ecosystem":"crates.io","package":"async-h1","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}],"bundled":2},{"source":"osv","ecosystem":"crates.io","package":"async-h1","ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-0"},{"fixed":"2.3.0"}]}],"bundled":2}],"products":[{"vendor":"rust-lang","product":"async-h1"}],"references":[{"url":"https://rustsec.org/advisories/RUSTSEC-2020-0093.html","tags":["x_refsource_MISC","x_transferred","Patch","Vendor Advisory","fix","web","advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-36202","tags":["advisory"]},{"url":"https://github.com/http-rs/async-h1/releases/tag/v2.3.0","tags":["advisory","web"]},{"url":"https://github.com/advisories/GHSA-c8rq-crxj-mj9m"},{"url":"https://github.com/http-rs/async-h1/security/advisories/GHSA-4vr9-8cjf-vf9c","tags":["advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-26281","tags":["advisory"]},{"url":"https://github.com/http-rs/async-h1","tags":["package"]},{"url":"https://crates.io/crates/async-h1","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2020-36202","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","status":"published","published":"2021-01-22T09:07:50Z","modified":"2024-08-04T17:23:09.493Z","updated_at":"2026-11-02T14:35:55.128961Z"}],"euvd":[{"id":"EUVD-2022-3538","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","status":"published","published":"2021-01-22T09:07:50Z","modified":"2024-08-04T17:23:09Z","updated_at":"2026-11-03T03:07:03.484914Z"}],"ghsa":[{"id":"GHSA-c8rq-crxj-mj9m","title":"Async-h1 request smuggling possible with long unread bodies","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","status":"published","published":"2022-05-24T17:40:15Z","modified":"2023-01-27T05:02:44Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:36:19.144959Z"}],"nvd":[{"id":"CVE-2020-36202","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","status":"published","published":"2021-01-26T18:15:55.49Z","modified":"2026-06-17T03:14:59.903Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary"},{"version":"2.0","score":4.3,"vector":"AV:N/AC:M/Au:N/C:N/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:06:30.596418Z"}],"osv":[{"id":"CVE-2020-26281","description":"async-h1 is an asynchronous HTTP/1.1 parser for Rust (crates.io). There is a request smuggling vulnerability in async-h1 before version 2.3.0. This vulnerability affects any webserver that uses async-h1 behind a reverse proxy, including all such Tide applications. If the server does not read the body of a request which is longer than some buffer length, async-h1 will attempt to read a subsequent request from the body content starting at that offset into the body. One way to exploit this vulnerability would be for an adversary to craft a request such that the body contains a request that would not be noticed by a reverse proxy, allowing it to forge forwarded/x-forwarded headers. If an application trusted the authenticity of these headers, it could be misled by the smuggled request. Another potential concern with this vulnerability is that if a reverse proxy is sending multiple http clients' requests along the same keep-alive connection, it would be possible for the smuggled request to specify a long content and capture another user's request in its body. This content could be captured in a post request to an endpoint that allows the content to be subsequently retrieved by the adversary. This has been addressed in async-h1 2.3.0 and previous versions have been yanked.","status":"published","published":"2020-12-21T22:15:13.407Z","modified":"2026-10-20T10:52:57.015672978Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:44:16.248747Z"},{"id":"CVE-2020-36202","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","status":"published","published":"2021-01-26T18:15:55.49Z","modified":"2026-10-24T10:30:51.581917961Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T15:44:16.612899Z"},{"id":"GHSA-4vr9-8cjf-vf9c","title":"Async-h1 request smuggling possible with long unread bodies","description":"### Impact\nThis vulnerability affects any webserver that uses async-h1 behind a reverse proxy, including all such Tide applications.\n\nIf the server does not read the body of a request which is longer than some buffer length, async-h1 will attempt to read a subsequent request from the body content starting at that offset into the body.\n\nOne way to exploit this vulnerability would be for an adversary to craft a request such that the body contains a request that would not be noticed by a reverse proxy, allowing it to forge forwarded/x-forwarded headers. If an application trusted the authenticity of these headers, it could be misled by the smuggled request.\n\nAnother potential concern with this vulnerability is that if a reverse proxy is sending multiple http clients' requests along the same keep-alive connection, it would be possible for the smuggled request to specify a long content and capture another user's request in its body. This content could be captured in a post request to an endpoint that allows the content to be subsequently retrieved by the adversary.\n\n\n### Patches\nThis has been addressed in async-h1 2.3.0 and previous versions have been yanked.\n\n### Workarounds\nnone\n\n### References\nhttps://github.com/http-rs/async-h1/releases/tag/v2.3.0\n\n### For more information\nIf you have any questions or comments about this advisory:\n* Open an issue in [async-h1](https://github.com/http-rs/async-h1)\n* Contact a core team member on [zulip](https://http-rs.zulip-chat.com) or [discord](https://discord.gg/x2gKzst)","status":"published","published":"2021-10-12T16:00:37Z","modified":"2026-09-10T03:49:08.929331849Z","cvss":[{"version":"3.1","score":6.8,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N","level":"medium"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:46:37.528068Z"},{"id":"GHSA-c8rq-crxj-mj9m","title":"Async-h1 request smuggling possible with long unread bodies","description":"An issue was discovered in the async-h1 crate before 2.3.0 for Rust. Request smuggling can occur when used behind a reverse proxy.","status":"published","published":"2022-05-24T17:40:15Z","modified":"2023-11-08T04:03:17.843075Z","cvss":[{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:46:44.927642Z"},{"id":"RUSTSEC-2020-0093","title":"Async-h1 request smuggling possible with long unread bodies","description":"This vulnerability affects any webserver that uses async-h1 behind a reverse proxy, including all such Tide applications.\n\nIf the server does not read the body of a request which is longer than some buffer length, async-h1 will attempt to read a subsequent request from the body content starting at that offset into the body.\n\nOne way to exploit this vulnerability would be for an adversary to craft a request such that the body contains a request that would not be noticed by a reverse proxy, allowing it to forge forwarded/x-forwarded headers. If an application trusted the authenticity of these headers, it could be misled by the smuggled request.\n\nAnother potential concern with this vulnerability is that if a reverse proxy is sending multiple http clients' requests along the same keep-alive connection, it would be possible for the smuggled request to specify a long content and capture another user's request in its body. This content could be captured in a post request to an endpoint that allows the content to be subsequently retrieved by the adversary.\n\nThe flaw was corrected in commit [7df79f](https://github.com/http-rs/async-h1/commit/7df79f1d5d99fc0f492b315eebc7f0d301a85212) by ensuring that the request body is always consumed from the tcp stream before attempting to read subsequent keep-alive request headers from it.","status":"published","published":"2020-12-17T12:00:00Z","modified":"2023-11-08T04:03:17.843075Z","updated_at":"2026-11-02T15:53:39.492624Z"}]}}