diff --git a/ext/standard/http.c b/ext/standard/http.c
index 9e070ee74f4..47443f74ffe 100644
--- a/ext/standard/http.c
+++ b/ext/standard/http.c
@@ -83,6 +83,15 @@ try_again:
 	}
 }
 
+static zend_always_inline bool php_url_check_stack_limit(void)
+{
+#ifdef ZEND_CHECK_STACK_LIMIT
+	return zend_call_stack_overflowed(EG(stack_limit));
+#else
+	return false;
+#endif
+}
+
 /* {{{ php_url_encode_hash */
 PHPAPI void php_url_encode_hash_ex(HashTable *ht, smart_str *formstr,
 				const char *num_prefix, size_t num_prefix_len,
@@ -101,6 +110,12 @@ PHPAPI void php_url_encode_hash_ex(HashTable *ht, smart_str *formstr,
 		return;
 	}
 
+	/* Very deeply structured data could trigger a stack overflow, even without recursion. */
+	if (UNEXPECTED(php_url_check_stack_limit())) {
+		zend_throw_error(NULL, "Maximum call stack size reached.");
+		return;
+	}
+
 	if (!arg_sep) {
 		arg_sep = PG(arg_separator).output;
 		if (ZSTR_LEN(arg_sep) == 0) {
diff --git a/ext/standard/image.c b/ext/standard/image.c
index 4eadace55ec..08cf8983d02 100644
--- a/ext/standard/image.c
+++ b/ext/standard/image.c
@@ -406,6 +406,7 @@ static size_t php_read_stream_all_chunks(php_stream *stream, char *buffer, size_
 		if (read_now < stream->chunk_size && read_total != length) {
 			return 0;
 		}
+		buffer += read_now;
 	} while (read_total < length);
 
 	return read_total;
diff --git a/ext/standard/tests/http/http_build_query/gh20583.phpt b/ext/standard/tests/http/http_build_query/gh20583.phpt
new file mode 100644
index 00000000000..c0331a830b1
--- /dev/null
+++ b/ext/standard/tests/http/http_build_query/gh20583.phpt
@@ -0,0 +1,27 @@
+--TEST--
+GH-20583 (Stack overflow in http_build_query via deep structures)
+--SKIPIF--
+<?php
+if (ini_get('zend.max_allowed_stack_size') === false) {
+    die('skip No stack limit support');
+}
+if (getenv('SKIP_ASAN')) {
+    die('skip ASAN needs different stack limit setting due to more stack space usage');
+}
+?>
+--INI--
+zend.max_allowed_stack_size=512K
+--FILE--
+<?php
+$a = null;
+for ($i = 0; $i < 5000; $i++) {
+ $a = [$i => $a];
+}
+try {
+    http_build_query($a, 'p');
+} catch (Throwable $e) {
+    echo $e::class, ": ", $e->getMessage(), "\n";
+}
+?>
+--EXPECT--
+Error: Maximum call stack size reached.
diff --git a/ext/standard/tests/image/gh20584.phpt b/ext/standard/tests/image/gh20584.phpt
new file mode 100644
index 00000000000..d117f218202
--- /dev/null
+++ b/ext/standard/tests/image/gh20584.phpt
@@ -0,0 +1,39 @@
+--TEST--
+GH-20584 (Information Leak of Memory)
+--CREDITS--
+Nikita Sveshnikov (Positive Technologies)
+--FILE--
+<?php
+// Minimal PoC: corruption/uninitialized memory leak when reading APP1 via php://filter
+$file = __DIR__ . '/gh20584.jpg';
+
+// Make APP1 large enough so it is read in multiple chunks
+$chunk = 8192;
+$tail = 123;
+$payload = str_repeat('A', $chunk) . str_repeat('B', $chunk) . str_repeat('Z',
+$tail);
+$app1Len = 2 + strlen($payload);
+
+// Minimal JPEG: SOI + APP1 + SOF0(1x1) + EOI
+$sof = "\xFF\xC0" . pack('n', 11) . "\x08" . pack('n',1) . pack('n',1) .
+"\x01\x11\x00";
+$jpeg = "\xFF\xD8" . "\xFF\xE1" . pack('n', $app1Len) . $payload . $sof .
+"\xFF\xD9";
+file_put_contents($file, $jpeg);
+
+// Read through a filter to enforce multiple reads
+$src = 'php://filter/read=string.rot13|string.rot13/resource=' . $file;
+$info = null;
+@getimagesize($src, $info);
+$exp = $payload;
+$ret = $info['APP1'];
+
+var_dump($ret === $exp);
+
+?>
+--CLEAN--
+<?php
+@unlink(__DIR__ . '/gh20584.jpg');
+?>
+--EXPECT--
+bool(true)