{"id":"CVE-2020-26281","aliases":["CVE-2020-36202","GHSA-4vr9-8cjf-vf9c","GHSA-c8rq-crxj-mj9m","RUSTSEC-2020-0093"],"url":"https://o3.security/vulnerability/CVE-2020-26281","summary":"Async-h1 request smuggling possible with long unread bodies","details":"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.","published":"2020-12-21T22:15:13.407Z","modified":"2026-07-09T01:06:18.470739Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"async-h1","fixedVersion":"2.3.0"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/http-rs/async-h1/releases/tag/v2.3.0"},{"type":"ADVISORY","url":"https://github.com/http-rs/async-h1/security/advisories/GHSA-4vr9-8cjf-vf9c"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T01:06:18.470739Z"}}