diff --git a/index.js b/index.js
index 8de00e9..be9f625 100644
--- a/index.js
+++ b/index.js
@@ -8,5 +8,5 @@
  */
 
 export { ProxyHeadersAgent, ConnectError } from './lib/core/proxy-headers-agent.js';
-export { parseProxyUrl, parseTargetUrl, buildConnectRequest } from './lib/core/utils.js';
+export { parseProxyUrl, parseTargetUrl, buildConnectRequest, validateHeaderName, validateHeaderValue } from './lib/core/utils.js';
 export { parseConnectResponse, hasCompleteHeaders } from './lib/core/connect-parser.js';
diff --git a/lib/core/utils.js b/lib/core/utils.js
index 01e714b..fdadf1e 100644
--- a/lib/core/utils.js
+++ b/lib/core/utils.js
@@ -2,6 +2,40 @@
  * Utility functions for proxy header handling.
  */
 
+const INVALID_HEADER_CHAR = /[\r\n\0]/;
+
+/**
+ * Validate that a header name does not contain characters that could
+ * enable CRLF injection in raw HTTP protocol strings.
+ * @param {string} name - Header name
+ * @throws {TypeError} If the name contains CR, LF, or NUL
+ */
+export function validateHeaderName(name) {
+    if (typeof name !== 'string' || name.length === 0) {
+        throw new TypeError('Header name must be a non-empty string');
+    }
+    if (INVALID_HEADER_CHAR.test(name)) {
+        throw new TypeError(
+            `Invalid character in header name: ${JSON.stringify(name.slice(0, 50))}`
+        );
+    }
+}
+
+/**
+ * Validate that a header value does not contain characters that could
+ * enable CRLF injection in raw HTTP protocol strings.
+ * @param {string} value - Header value
+ * @throws {TypeError} If the value contains CR, LF, or NUL
+ */
+export function validateHeaderValue(value) {
+    const str = String(value);
+    if (INVALID_HEADER_CHAR.test(str)) {
+        throw new TypeError(
+            `Invalid character in header value: ${JSON.stringify(str.slice(0, 50))}`
+        );
+    }
+}
+
 /**
  * Parse a proxy URL into components.
  * @param {string|URL} proxyUrl - The proxy URL
@@ -60,6 +94,8 @@ export function buildConnectRequest(targetHost, targetPort, proxyAuth, proxyHead
         ? [...proxyHeaders.entries()]
         : Object.entries(proxyHeaders || {});
     for (const [key, value] of entries) {
+        validateHeaderName(key);
+        validateHeaderValue(value);
         lines.push(`${key}: ${value}`);
     }