diff --git a/NEWS b/NEWS
index bf80ab696b09..1984a4a81dc5 100644
--- a/NEWS
+++ b/NEWS
@@ -25,6 +25,8 @@ PHP                                                                        NEWS
     (timwolla)
   . Fixed double-free when assigning to $errors fails when using
     the Uri\WhatWg\Url parser. (timwolla)
+  . Reject out-of-range ports when using the Uri\Rfc3986\Uri parser.
+    (timwolla)
   . Clean up naming of internal API. (timwolla)
 
 28 Aug 2025, PHP 8.5.0beta2
diff --git a/ext/uri/tests/058.phpt b/ext/uri/tests/058.phpt
new file mode 100644
index 000000000000..efca0a0e8aaf
--- /dev/null
+++ b/ext/uri/tests/058.phpt
@@ -0,0 +1,32 @@
+--TEST--
+Test that integer overflows in the port are rejected
+--EXTENSIONS--
+uri
+--FILE--
+<?php
+
+if (PHP_INT_SIZE == 8) {
+    $uri = new \Uri\Rfc3986\Uri('https://example.com:9223372036854775807');
+    echo $uri->getPort(), PHP_EOL;
+    echo "2147483647", PHP_EOL;
+} else {
+    $uri = new \Uri\Rfc3986\Uri('https://example.com:2147483647');
+    echo "9223372036854775807", PHP_EOL;
+    echo $uri->getPort(), PHP_EOL;
+}
+
+try {
+    if (PHP_INT_SIZE == 8) {
+        new \Uri\Rfc3986\Uri('https://example.com:9223372036854775808');
+    } else {
+        new \Uri\Rfc3986\Uri('https://example.com:2147483648');
+    }
+} catch (Throwable $e) {
+    echo $e::class, ": ", $e->getMessage(), PHP_EOL;
+}
+
+?>
+--EXPECT--
+9223372036854775807
+2147483647
+Uri\InvalidUriException: The port is out of range
diff --git a/ext/uri/uri_parser_rfc3986.c b/ext/uri/uri_parser_rfc3986.c
index cf7235b071b4..f9581e6d93ed 100644
--- a/ext/uri/uri_parser_rfc3986.c
+++ b/ext/uri/uri_parser_rfc3986.c
@@ -190,15 +190,22 @@ ZEND_ATTRIBUTE_NONNULL static zend_result php_uri_parser_rfc3986_host_read(const
 	return SUCCESS;
 }
 
-ZEND_ATTRIBUTE_NONNULL static size_t str_to_int(const char *str, size_t len)
+ZEND_ATTRIBUTE_NONNULL static zend_long port_str_to_zend_long_checked(const char *str, size_t len)
 {
-	size_t result = 0;
+	if (len > MAX_LENGTH_OF_LONG) {
+		return -1;
+	}
+
+	char buf[MAX_LENGTH_OF_LONG + 1];
+	*(char*)zend_mempcpy(buf, str, len) = 0;
+
+	zend_ulong result = ZEND_STRTOUL(buf, NULL, 10);
 
-	for (size_t i = 0; i < len; ++i) {
-		result = result * 10 + (str[i] - '0');
+	if (result > ZEND_LONG_MAX) {
+		return -1;
 	}
 
-	return result;
+	return (zend_long)result;
 }
 
 ZEND_ATTRIBUTE_NONNULL static zend_result php_uri_parser_rfc3986_port_read(const uri_internal_t *internal_uri, uri_component_read_mode_t read_mode, zval *retval)
@@ -206,7 +213,7 @@ ZEND_ATTRIBUTE_NONNULL static zend_result php_uri_parser_rfc3986_port_read(const
 	const UriUriA *uriparser_uri = get_uri_for_reading(internal_uri->uri, read_mode);
 
 	if (has_text_range(&uriparser_uri->portText)) {
-		ZVAL_LONG(retval, str_to_int(uriparser_uri->portText.first, get_text_range_length(&uriparser_uri->portText)));
+		ZVAL_LONG(retval, port_str_to_zend_long_checked(uriparser_uri->portText.first, get_text_range_length(&uriparser_uri->portText)));
 	} else {
 		ZVAL_NULL(retval);
 	}
@@ -319,6 +326,17 @@ php_uri_parser_rfc3986_uris *php_uri_parser_rfc3986_parse_ex(const char *uri_str
 	/* Make the resulting URI independent of the 'uri_str'. */
 	uriMakeOwnerMmA(&uri, mm);
 
+	if (
+		has_text_range(&uri.portText)
+		&& port_str_to_zend_long_checked(uri.portText.first, get_text_range_length(&uri.portText)) == -1
+	) {
+		if (!silent) {
+			zend_throw_exception(uri_invalid_uri_exception_ce, "The port is out of range", 0);
+		}
+
+		goto fail;
+	}
+
 	php_uri_parser_rfc3986_uris *uriparser_uris = uriparser_create_uris();
 	uriparser_uris->uri = uri;