title: request smuggling in async-h1
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.
problem types: CWE-444: Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')
affected:
{
product: async-h1
vendor: http-rs
versions:
status: affected, version: < 2.3.0
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: NONE
baseScore: 6.8
baseSeverity: MEDIUM
confidentialityImpact: NONE
integrityImpact: HIGH
privilegesRequired: NONE
scope: CHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N
version: 3.1
]