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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLWYzcGctcXd2Zy1wOTlj
Lenient Parsing of Content-Length Header When Prefixed with Plus Sign
Summary
hyper's HTTP/1 server code had a flaw that incorrectly parses and accepts requests with a Content-Length
header with a prefixed plus sign, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that doesn't parse such Content-Length
headers, but forwards them, can result in "request smuggling" or "desync attacks".
Vulnerability
The flaw exists in all prior versions of hyper, if built with rustc
v1.5.0 or newer.
Example:
GET / HTTP/1.1
Host: example.com
Content-Length: +3
abc
This request gets accepted and hyper reads the body as abc. The request should be rejected, according to RFC 7230, since the ABNF for Content-Length
only allows for DIGIT
s. This is due to using the FromStr
implementation for u64
in the standard library. By differing from the spec, it is possible to send requests like these to endpoints that have different HTTP implementations, with different interpretations of the payload semantics, and cause "desync attacks".
In this particular case, an upstream proxy would need to error when parsing the Content-Length
, but not reject the request (swallowing its own error), and forwarding the request as-is with the Content-Length
still included. Then the upstream proxy and hyper would disagree on the length of the request body. The combination of these factors would be extremely rare.
Read more about desync attacks: https://portswigger.net/research/http-desync-attacks-request-smuggling-reborn
Impact
To determine if vulnerable, all these things must be true:
- Using hyper as an HTTP server. While the lenient decoder also exists in the client, a vulnerability does not exist around responses.
- Using HTTP/1. The HTTP/2 code uses a stricter parser.
- Using a vulnerable HTTP proxy upstream to hyper. If an upstream proxy correctly rejects the illegal
Content-Length
header, OR can parse the length with the plus sign, the desync attack cannot succeed.
Patches
We have released the following patch versions:
- v0.14.10 (to be released when this advisor is published)
Workarounds
Besides upgrading hyper, you can take the following options:
- Reject requests manually that contain a plus sign prefix in the
Content-Length
header. - Ensure any upstream proxy handles
Content-Length
headers with a plus sign prefix.
Credits
This issue was initially reported by Mattias Grenfeldt and Asta Olofsson.
Permalink: https://github.com/advisories/GHSA-f3pg-qwvg-p99cJSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLWYzcGctcXd2Zy1wOTlj
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Low
Classification: General
Published: almost 3 years ago
Updated: about 1 year ago
CVSS Score: 3.1
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:N/A:N
Identifiers: GHSA-f3pg-qwvg-p99c, CVE-2021-32715
References:
- https://github.com/hyperium/hyper/security/advisories/GHSA-f3pg-qwvg-p99c
- https://nvd.nist.gov/vuln/detail/CVE-2021-32715
- https://github.com/rust-lang/rust/pull/28826/commits/123a83326fb95366e94a3be1a74775df4db97739
- https://rustsec.org/advisories/RUSTSEC-2021-0078.html
- https://github.com/hyperium/hyper/commit/1fb719e0b61a4f3d911562a436a2ff05fd7cb759
- https://github.com/advisories/GHSA-f3pg-qwvg-p99c
Blast Radius: 14.2
Affected Packages
cargo:hyper
Dependent packages: 3,673Dependent repositories: 38,106
Downloads: 144,045,445 total
Affected Version Ranges: < 0.14.10
Fixed in: 0.14.10
All affected versions: 0.0.1, 0.0.2, 0.0.3, 0.0.4, 0.0.5, 0.0.6, 0.0.7, 0.0.8, 0.0.9, 0.0.10, 0.0.11, 0.0.12, 0.0.13, 0.0.14, 0.0.15, 0.0.16, 0.0.17, 0.0.18, 0.0.19, 0.0.20, 0.0.21, 0.1.0, 0.1.1, 0.1.2, 0.1.3, 0.1.4, 0.1.5, 0.1.6, 0.1.7, 0.1.8, 0.1.9, 0.1.10, 0.1.11, 0.1.12, 0.1.13, 0.2.0, 0.2.1, 0.3.0, 0.3.1, 0.3.2, 0.3.3, 0.3.4, 0.3.5, 0.3.6, 0.3.7, 0.3.8, 0.3.9, 0.3.10, 0.3.11, 0.3.12, 0.3.13, 0.3.14, 0.3.15, 0.3.16, 0.4.0, 0.5.0, 0.5.1, 0.5.2, 0.6.0, 0.6.1, 0.6.2, 0.6.3, 0.6.4, 0.6.5, 0.6.6, 0.6.7, 0.6.8, 0.6.9, 0.6.10, 0.6.11, 0.6.12, 0.6.13, 0.6.14, 0.6.15, 0.6.16, 0.7.0, 0.7.1, 0.7.2, 0.8.0, 0.8.1, 0.9.0, 0.9.1, 0.9.2, 0.9.3, 0.9.4, 0.9.5, 0.9.6, 0.9.7, 0.9.8, 0.9.9, 0.9.10, 0.9.11, 0.9.12, 0.9.13, 0.9.14, 0.9.15, 0.9.17, 0.9.18, 0.10.0, 0.10.1, 0.10.2, 0.10.3, 0.10.4, 0.10.5, 0.10.6, 0.10.7, 0.10.8, 0.10.9, 0.10.10, 0.10.11, 0.10.12, 0.10.13, 0.10.14, 0.10.15, 0.10.16, 0.11.0, 0.11.1, 0.11.2, 0.11.3, 0.11.4, 0.11.5, 0.11.6, 0.11.7, 0.11.8, 0.11.9, 0.11.10, 0.11.11, 0.11.12, 0.11.13, 0.11.14, 0.11.15, 0.11.16, 0.11.17, 0.11.18, 0.11.19, 0.11.20, 0.11.21, 0.11.22, 0.11.23, 0.11.24, 0.11.25, 0.11.26, 0.11.27, 0.12.0, 0.12.1, 0.12.2, 0.12.3, 0.12.4, 0.12.5, 0.12.6, 0.12.7, 0.12.8, 0.12.9, 0.12.10, 0.12.11, 0.12.12, 0.12.13, 0.12.14, 0.12.15, 0.12.16, 0.12.17, 0.12.18, 0.12.19, 0.12.20, 0.12.21, 0.12.22, 0.12.23, 0.12.24, 0.12.25, 0.12.26, 0.12.27, 0.12.28, 0.12.29, 0.12.30, 0.12.31, 0.12.32, 0.12.33, 0.12.34, 0.12.35, 0.12.36, 0.13.0, 0.13.1, 0.13.2, 0.13.3, 0.13.4, 0.13.5, 0.13.6, 0.13.7, 0.13.8, 0.13.9, 0.13.10, 0.14.0, 0.14.1, 0.14.2, 0.14.3, 0.14.4, 0.14.5, 0.14.6, 0.14.7, 0.14.8, 0.14.9
All unaffected versions: 0.14.10, 0.14.11, 0.14.12, 0.14.13, 0.14.14, 0.14.15, 0.14.16, 0.14.17, 0.14.18, 0.14.19, 0.14.20, 0.14.21, 0.14.22, 0.14.23, 0.14.24, 0.14.25, 0.14.26, 0.14.27, 0.14.28, 1.0.0, 1.0.1, 1.1.0, 1.2.0, 1.3.0, 1.3.1