From dcc46710f742e29710a0a68fa2bd29975bde0019 Mon Sep 17 00:00:00 2001
From: Ashish Sharma <ashish.sharma@espressif.com>
Date: Fri, 27 Mar 2026 15:07:56 +0800
Subject: [PATCH] feat(esp_http_server): adds check for crlf in response
 creation

---
 components/esp_http_server/src/httpd_txrx.c   | 20 +++++++++-
 .../test_apps/main/test_http_server.c         | 37 ++++++++++++++++++-
 2 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/components/esp_http_server/src/httpd_txrx.c b/components/esp_http_server/src/httpd_txrx.c
index 7171de145c3..a8bd89cdf2b 100644
--- a/components/esp_http_server/src/httpd_txrx.c
+++ b/components/esp_http_server/src/httpd_txrx.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2018-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2018-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -170,6 +170,12 @@ esp_err_t httpd_resp_set_hdr(httpd_req_t *r, const char *field, const char *valu
         return ESP_ERR_HTTPD_INVALID_REQ;
     }
 
+    /* Reject CRLF in header field or value */
+    if (strpbrk(field, "\r\n") || strpbrk(value, "\r\n")) {
+        ESP_LOGW(TAG, LOG_FMT("rejecting header with CRLF: %.32s"), field);
+        return ESP_ERR_INVALID_ARG;
+    }
+
     struct httpd_req_aux *ra = r->aux;
     struct httpd_data *hd = (struct httpd_data *) r->handle;
 
@@ -201,6 +207,12 @@ esp_err_t httpd_resp_set_status(httpd_req_t *r, const char *status)
         return ESP_ERR_HTTPD_INVALID_REQ;
     }
 
+    /* Reject CRLF in status */
+    if (strpbrk(status, "\r\n")) {
+        ESP_LOGW(TAG, LOG_FMT("rejecting status with CRLF: %.32s"), status);
+        return ESP_ERR_INVALID_ARG;
+    }
+
     struct httpd_req_aux *ra = r->aux;
     ra->status = (char *)status;
     return ESP_OK;
@@ -220,6 +232,12 @@ esp_err_t httpd_resp_set_type(httpd_req_t *r, const char *type)
         return ESP_ERR_HTTPD_INVALID_REQ;
     }
 
+    /* Reject CRLF in content type */
+    if (strpbrk(type, "\r\n")) {
+        ESP_LOGW(TAG, LOG_FMT("rejecting content type with CRLF: %.32s"), type);
+        return ESP_ERR_INVALID_ARG;
+    }
+
     struct httpd_req_aux *ra = r->aux;
     ra->content_type = (char *)type;
     return ESP_OK;
diff --git a/components/esp_http_server/test_apps/main/test_http_server.c b/components/esp_http_server/test_apps/main/test_http_server.c
index 0acb8c9ed40..e7edf35cc35 100644
--- a/components/esp_http_server/test_apps/main/test_http_server.c
+++ b/components/esp_http_server/test_apps/main/test_http_server.c
@@ -100,7 +100,7 @@ httpd_handle_t test_httpd_start(uint16_t id)
 
 /* Currently this only tests for the number of tasks.
  * Heap leakage is not tested as LWIP allocates memory
- * which may not be freed immedietly causing erroneous
+ * which may not be freed immediately causing erroneous
  * evaluation. Another test to implement would be the
  * monitoring of open sockets, but LWIP presently provides
  * no such API for getting the number of open sockets.
@@ -244,6 +244,41 @@ TEST_CASE("Max Allowed Sockets Test", "[HTTP SERVER]")
     TEST_ASSERT(httpd_start(&hd, &config) != ESP_OK);
 }
 
+TEST_CASE("httpd_resp_set_hdr rejects CRLF in header field and value", "[HTTP SERVER][security]")
+{
+    httpd_req_t fake_req = {0};
+
+    /* \r\n in value */
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_hdr(&fake_req, "X-Field", "val\r\nX-Injected: pwned"));
+    /* bare \n in value */
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_hdr(&fake_req, "X-Field", "val\nX-Injected: pwned"));
+    /* \r\n in field name */
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_hdr(&fake_req, "X-Field\r\nX-Injected: pwned", "val"));
+}
+
+TEST_CASE("httpd_resp_set_status rejects CRLF in status string", "[HTTP SERVER][security]")
+{
+    httpd_req_t fake_req = {0};
+
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_status(&fake_req, "200 OK\r\nX-Injected: pwned"));
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_status(&fake_req, "200 OK\nX-Injected: pwned"));
+}
+
+TEST_CASE("httpd_resp_set_type rejects CRLF in content type", "[HTTP SERVER][security]")
+{
+    httpd_req_t fake_req = {0};
+
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_type(&fake_req, "text/html\r\nX-Injected: pwned"));
+    TEST_ASSERT_EQUAL(ESP_ERR_INVALID_ARG,
+                      httpd_resp_set_type(&fake_req, "text/html\nX-Injected: pwned"));
+}
+
 void app_main(void)
 {
     unity_run_menu();