# CVE-2024-51501: CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes

> Attackers can inject CRLF characters into HTTP headers via Refit attributes, potentially enabling request splitting and Server-Side Request Forgery in consuming applications.

- **Severity:** Critical 10.0 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Nov 2024
- **Updated:** 8 Nov 2024
- **Also known as:** GHSA-3hxg-fxwm-8gf7

## What is CVE-2024-51501?

CVE-2024-51501 is a critical server-side request forgery vulnerability in reactiveui refit, published on 4 Nov 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Refit is an automatic type-safe REST library for .NET Core, Xamarin and .NET The various header-related Refit attributes (Header, HeaderCollection and Authorize) are vulnerable to CRLF injection. The way HTTP headers are added to a request is via the `HttpHeaders.TryAddWithoutValidation` method. 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. 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 and not in Refit itself. This issue has been addressed in release versions 7.2.22 and 8.0.0 and all users are advised to upgrade. There are no known workarounds for this vulnerability.

Weakness: CWE-93 (Improper Neutralization of CRLF Sequences)

## Which versions are affected by CVE-2024-51501?

2 open source packages ship an affected version, including Refit.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `Refit` | NuGet | All versions | 7.2.22 |
| `Refit` | NuGet | All versions | 7.2.22 |

## How do I fix CVE-2024-51501?

Upgrade Refit to 7.2.22 or later.

## Is CVE-2024-51501 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-51501 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-51501 and fix it if it is affected.

What it is: CVE-2024-51501 is a critical server-side request forgery vulnerability in reactiveui refit, published on 4 Nov 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2024-51501 exists.

Affected packages and fixed versions:
- Refit (NuGet): affected all versions; fixed in 7.2.22
- Refit (NuGet): affected all versions; fixed in 7.2.22

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-51501/ (Markdown: https://insights.sbomify.com/CVE-2024-51501/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-51501
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-51501
- OSV: https://osv.dev/vulnerability/CVE-2024-51501

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-51501/
Summaries are generated and may contain mistakes; the official description above is the record.