diff --git a/changelog.txt b/changelog.txt
index ac0bf00..d409588 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -29,6 +29,15 @@
 - fixed `attachmentfs()` in the mail: the file of the storage is read as a Buffer and the message is completed (it threw a `TypeError` and the SMTP connection stayed open)
 - fixed `attachment()` with a `Buffer` in the mail: the Base64 of the whole Buffer is split into lines (the bytes were split into pieces of 68 bytes and each one got its own padding)
 - fixed `@{hostname()}` view engine command
+- security: hardened the hostnames against the Node.js security release of 2026-10-21 (patched in Node.js 22.23.4, 24.22.1 and 26.12.1) ; the framework does not require a specific version of Node.js, the hostnames are normalized and validated in the framework itself
+	- CVE-2026-105482: `dns.resolve*()` truncates a name at a NUL byte (`attacker.example\0.trusted.example`)
+	- CVE-2026-105483, CVE-2026-106069, CVE-2026-106072: `tls.checkServerIdentity()` with IPv4 literals written with non-ASCII digits, leading zeros or in a non-canonical form (`0x7f.0.0.1`, `127.1`, `2130706433`)
+- added `U.validhost(host)` that accepts only plain hostnames and canonical IP literals
+- added `U.tohost(host)` that converts a hostname to the canonical ASCII form (punycode, dotted IPv4) and returns an empty string for an invalid hostname
+- fixed `U.resolve()` (used by `REQUEST()`): an invalid hostname gives an error before the DNS query
+- fixed `U.connect()`: the `host` is normalized and an invalid hostname gives the `Invalid hostname` error
+- fixed the SMTP `server` in the mail: the hostname is normalized (international names to punycode, IPv4 to the canonical form) and an invalid hostname gives the `Invalid SMTP server hostname.` error
+- note: the issue CVE-2026-105481 (unsolicited data on a reused keep-alive socket, `http.Agent`) is fixed only by updating Node.js ; the Brotli issue CVE-2026-111497 does not affect the framework (only `gzip` and `deflate` are decompressed)
 
 ========================
 0.0.19
diff --git a/mail.js b/mail.js
index a17f838..4186328 100755
--- a/mail.js
+++ b/mail.js
@@ -477,8 +477,13 @@ Mailer.send = function(opt, messages, callback) {
 	if (opt.secure && !opt.port)
 		opt.port = 465;
 
-	if (!opt.server)  {
-		const err = new Error('No SMTP server configuration.');
+	const server = opt.server ? F.TUtils.tohost(opt.server) : '';
+
+	if (server && server !== opt.server)
+		opt = Object.assign({}, opt, { server: server });
+
+	if (!server)  {
+		const err = new Error(opt.server ? 'Invalid SMTP server hostname.' : 'No SMTP server configuration.');
 		let iscallback = false;
 
 		if (callback) {
diff --git a/utils.js b/utils.js
index 49a94b8..6f675f9 100755
--- a/utils.js
+++ b/utils.js
@@ -489,12 +489,41 @@ exports.toURLEncode = function(value) {
 	return builder.length ? builder.join('&') : '';
 };
 
+const REG_HOST_NUMERIC = /^(0x[0-9a-f]+|[0-9]+)(\.(0x[0-9a-f]+|[0-9]+))*$/i;
+const REG_HOST_IPV4 = /^((25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9]?[0-9])$/;
+
+// Accepts plain hostnames and canonical IP literals only. It rejects NUL bytes, non-ASCII characters
+// and non-canonical IPv4 forms (0127.0.0.1, 0x7f.1, 2130706433, 127.1) which Node.js, certificate
+// checks and the OS can interpret differently.
+exports.validhost = function(host) {
+
+	if (!host || typeof(host) !== 'string' || /[^\x21-\x7e]/.test(host))
+		return false;
+
+	return REG_HOST_NUMERIC.test(host) ? REG_HOST_IPV4.test(host) : true;
+};
+
+// Converts a host to its canonical ASCII form (punycode for international names, canonical dotted IPv4)
+// and returns an empty string when the host is not valid.
+exports.tohost = function(host) {
+
+	if (!host || typeof(host) !== 'string')
+		return '';
+
+	if (host.indexOf(':') === -1)
+		host = F.Url.domainToASCII(host);
+
+	return exports.validhost(host) ? host : '';
+};
+
 exports.resolve = function(url, callback, param) {
 
 	let uri;
 
 	try {
 		uri = exports.parseURI(url);
+		if (!exports.validhost(uri.hostname))
+			throw new Error('Invalid hostname');
 	} catch (e) {
 		callback(e);
 		return;
@@ -5921,6 +5950,15 @@ exports.connect = function(opt, callback) {
 
 	delete opt.tls;
 
+	if (opt.host) {
+		opt.host = exports.tohost(opt.host);
+		if (!opt.host) {
+			meta.destroy = meta.close = NOOP;
+			callback && setImmediate(callback, new Error('Invalid hostname'));
+			return meta;
+		}
+	}
+
 	var close = function() {
 
 		if (meta.socket1) {