CVE-2021-21299 Information

Description

hyper is an open-source HTTP library for Rust (crates.io). In hyper from version 0.12.0 and before versions 0.13.10 and 0.14.3 there is a vulnerability that can enable a request smuggling attack. The HTTP server code had a flaw that incorrectly understands some requests with multiple transfer-encoding headers to have a chunked payload when it should have been rejected as illegal. This combined with an upstream HTTP proxy that understands the request payload boundary differently can result in equest smuggling\ or \desync attacks. To determine if vulnerable all these things must be true: 1) Using hyper as an HTTP server (the client is not affected) 2) Using HTTP/1.1 (HTTP/2 does not use transfer-encoding) 3) Using a vulnerable HTTP proxy upstream to hyper. If an upstream proxy correctly rejects the illegal transfer-encoding headers the desync attack cannot succeed. If there is no proxy upstream of hyper hyper cannot start the desync attack as the client will repair the headers before forwarding. This is fixed in versions 0.14.3 and 0.13.10. As a workaround one can take the following options: 1) Reject requests that contain a transfer-encoding header 2) Ensure any upstream proxy handles transfer-encoding correctly.

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Reference

https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn https://github.com/hyperium/hyper/commit/8f93123efef5c1361086688fe4f34c83c89cec02 https://crates.io/crates/hyper https://github.com/hyperium/hyper/security/advisories/GHSA-6hfq-h8hq-87mf https://rustsec.org/advisories/RUSTSEC-2021-0020.html

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.1