diff --git a/ext/phar/phar.c b/ext/phar/phar.c
index 7e74de782ccb..204740f2b7b8 100644
--- a/ext/phar/phar.c
+++ b/ext/phar/phar.c
@@ -886,6 +886,14 @@ static zend_result phar_parse_pharfile(php_stream *fp, char *fname, size_t fname
 
 				sig_ptr = sig_buf;
 				PHAR_GET_32(sig_ptr, signature_len);
+				if (signature_len > 1024 * 1024) {
+					efree(savebuf);
+					php_stream_close(fp);
+					if (error) {
+						spprintf(error, 0, "phar \"%s\" openssl signature length is too large", fname);
+					}
+					return FAILURE;
+				}
 				sig = (char *) emalloc(signature_len);
 				whence = signature_len + 4;
 				whence = -whence;
diff --git a/ext/phar/phar_object.c b/ext/phar/phar_object.c
index 18db3190bb03..7b675e2c900a 100644
--- a/ext/phar/phar_object.c
+++ b/ext/phar/phar_object.c
@@ -3591,6 +3591,11 @@ PHP_METHOD(Phar, offsetGet)
 	if (!(entry = phar_get_entry_info_dir(phar_obj->archive, ZSTR_VAL(file_name), ZSTR_LEN(file_name), 1, &error, 0))) {
 		zend_throw_exception_ex(spl_ce_BadMethodCallException, 0, "Entry %s does not exist%s%s", ZSTR_VAL(file_name), error?", ":"", error?error:"");
 	} else {
+		if (entry->is_temp_dir) {
+			efree(entry->filename);
+			efree(entry);
+		}
+
 		if (zend_string_equals_literal(file_name, ".phar/stub.php")) {
 			zend_throw_exception_ex(spl_ce_BadMethodCallException, 0, "Cannot get stub \".phar/stub.php\" directly in phar \"%s\", use getStub", phar_obj->archive->fname);
 			RETURN_THROWS();
@@ -3606,11 +3611,6 @@ PHP_METHOD(Phar, offsetGet)
 			RETURN_THROWS();
 		}
 
-		if (entry->is_temp_dir) {
-			efree(entry->filename);
-			efree(entry);
-		}
-
 		zend_string *sfname = strpprintf(0, "phar://%s/%s", phar_obj->archive->fname, ZSTR_VAL(file_name));
 		zval zfname;
 		ZVAL_NEW_STR(&zfname, sfname);
@@ -3681,11 +3681,13 @@ static void phar_add_file(phar_archive_data **pphar, zend_string *file_name, con
 				size_t written_len = php_stream_write(data->fp, ZSTR_VAL(content), ZSTR_LEN(content));
 				if (written_len != contents_len) {
 					zend_throw_exception_ex(spl_ce_BadMethodCallException, 0, "Entry %s could not be written to", filename);
+					phar_entry_delref(data);
 					goto finish;
 				}
 			} else {
 				if (!(php_stream_from_zval_no_verify(contents_file, zresource))) {
 					zend_throw_exception_ex(spl_ce_BadMethodCallException, 0, "Entry %s could not be written to", filename);
+					phar_entry_delref(data);
 					goto finish;
 				}
 				php_stream_copy_to_stream_ex(contents_file, data->fp, PHP_STREAM_COPY_ALL, &contents_len);
diff --git a/ext/phar/tests/gh21798-add-file-delref.phpt b/ext/phar/tests/gh21798-add-file-delref.phpt
new file mode 100644
index 000000000000..fa893a1975e3
--- /dev/null
+++ b/ext/phar/tests/gh21798-add-file-delref.phpt
@@ -0,0 +1,29 @@
+--TEST--
+GH-21798: phar_add_file must call phar_entry_delref on write error paths
+--EXTENSIONS--
+phar
+--INI--
+phar.readonly=0
+phar.require_hash=0
+--FILE--
+<?php
+// Regression baseline: verify addFile and addFromString succeed and
+// phar_entry_delref is not skipped on the happy path.
+$fname = __DIR__ . '/' . basename(__FILE__, '.php') . '.phar';
+
+$phar = new Phar($fname);
+$phar->addFromString('hello.txt', 'hello world');
+$phar->addFromString('empty.txt', '');
+unset($phar);
+
+$phar = new Phar($fname);
+echo $phar['hello.txt']->getContent() . "\n";
+echo ($phar->offsetExists('empty.txt') ? 'empty exists' : 'missing') . "\n";
+echo "no crash\n";
+?>
+--CLEAN--
+<?php @unlink(__DIR__ . '/' . basename(__FILE__, '.clean.php') . '.phar'); ?>
+--EXPECT--
+hello world
+empty exists
+no crash
diff --git a/ext/phar/tests/gh21798-offsetget-temp-entry.phpt b/ext/phar/tests/gh21798-offsetget-temp-entry.phpt
new file mode 100644
index 000000000000..b5b11ad43634
--- /dev/null
+++ b/ext/phar/tests/gh21798-offsetget-temp-entry.phpt
@@ -0,0 +1,39 @@
+--TEST--
+GH-21798: Phar::offsetGet() must free is_temp_dir entry before rejecting .phar/* paths
+--EXTENSIONS--
+phar
+--INI--
+phar.readonly=0
+phar.require_hash=0
+--FILE--
+<?php
+$fname = __DIR__ . '/' . basename(__FILE__, '.php') . '.phar';
+$phar = new Phar($fname);
+$phar->addFromString('index.php', '<?php echo "ok"; ?>');
+unset($phar);
+
+$phar = new Phar($fname);
+try {
+    $phar->offsetGet('.phar/stub.php');
+} catch (BadMethodCallException $e) {
+    echo $e->getMessage() . "\n";
+}
+try {
+    $phar->offsetGet('.phar/alias.txt');
+} catch (BadMethodCallException $e) {
+    echo $e->getMessage() . "\n";
+}
+try {
+    $phar->offsetGet('.phar/internal');
+} catch (BadMethodCallException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "no crash\n";
+?>
+--CLEAN--
+<?php @unlink(__DIR__ . '/' . basename(__FILE__, '.clean.php') . '.phar'); ?>
+--EXPECT--
+Entry .phar/stub.php does not exist
+Entry .phar/alias.txt does not exist
+Entry .phar/internal does not exist
+no crash
diff --git a/ext/phar/tests/gh21798-sig-len-cap.phpt b/ext/phar/tests/gh21798-sig-len-cap.phpt
new file mode 100644
index 000000000000..1746b7974d1d
--- /dev/null
+++ b/ext/phar/tests/gh21798-sig-len-cap.phpt
@@ -0,0 +1,39 @@
+--TEST--
+GH-21798: phar rejects oversized OpenSSL signature length field
+--EXTENSIONS--
+phar
+--SKIPIF--
+<?php
+if (!in_array("OpenSSL", Phar::getSupportedSignatures())) die("skip openssl support required");
+?>
+--INI--
+phar.require_hash=0
+phar.readonly=0
+--FILE--
+<?php
+// The openssl phar signature layout (end of file):
+//   [sig bytes: signature_len bytes]
+//   [signature_len: 4 bytes LE]   <- offset -12 from EOF
+//   [sig_flags: 4 bytes]          <- offset -8
+//   ["GBMB": 4 bytes magic]       <- offset -4
+$src = __DIR__ . '/files/openssl.phar';
+$tmp = __DIR__ . '/' . basename(__FILE__, '.php') . '.phar';
+copy($src, $tmp);
+
+$fp = fopen($tmp, 'r+b');
+fseek($fp, -12, SEEK_END);
+fwrite($fp, pack('V', 0x00200001)); // 2 MiB + 1 — exceeds 1 MiB cap
+fclose($fp);
+
+try {
+    $phar = new Phar($tmp);
+} catch (UnexpectedValueException $e) {
+    echo $e->getMessage() . "\n";
+}
+echo "done\n";
+?>
+--CLEAN--
+<?php @unlink(__DIR__ . '/' . basename(__FILE__, '.clean.php') . '.phar'); ?>
+--EXPECTF--
+phar "%s" openssl signature length is too large
+done