diff --git a/apps/dav/lib/Comments/EntityCollection.php b/apps/dav/lib/Comments/EntityCollection.php
index 19af2d9c23401..7c120a37a8479 100644
--- a/apps/dav/lib/Comments/EntityCollection.php
+++ b/apps/dav/lib/Comments/EntityCollection.php
@@ -84,6 +84,10 @@ public function getId() {
 	public function getChild($name) {
 		try {
 			$comment = $this->commentsManager->get($name);
+			if ($comment->getObjectType() !== $this->name
+				|| $comment->getObjectId() !== $this->id) {
+				throw new NotFound();
+			}
 			return new CommentNode(
 				$this->commentsManager,
 				$comment,
@@ -137,8 +141,9 @@ public function findChildren($limit = 0, $offset = 0, ?\DateTime $datetime = nul
 	 */
 	public function childExists($name) {
 		try {
-			$this->commentsManager->get($name);
-			return true;
+			$comment = $this->commentsManager->get($name);
+			return $comment->getObjectType() === $this->name
+				&& $comment->getObjectId() === $this->id;
 		} catch (NotFoundException $e) {
 			return false;
 		}
diff --git a/apps/dav/tests/unit/Comments/EntityCollectionTest.php b/apps/dav/tests/unit/Comments/EntityCollectionTest.php
index 0d4adae250ed9..8c417aeabca89 100644
--- a/apps/dav/tests/unit/Comments/EntityCollectionTest.php
+++ b/apps/dav/tests/unit/Comments/EntityCollectionTest.php
@@ -58,14 +58,16 @@ public function testGetId(): void {
 	}
 
 	public function testGetChild(): void {
+		$comment = $this->createMock(IComment::class);
+		$comment->method('getObjectType')
+			->willReturn('files');
+		$comment->method('getObjectId')
+			->willReturn('19');
+
 		$this->commentsManager->expects($this->once())
 			->method('get')
 			->with('55')
-			->willReturn(
-				$this->getMockBuilder(IComment::class)
-					->disableOriginalConstructor()
-					->getMock()
-			);
+			->willReturn($comment);
 
 		$node = $this->collection->getChild('55');
 		$this->assertTrue($node instanceof \OCA\DAV\Comments\CommentNode);
@@ -117,6 +119,17 @@ public function testFindChildren(): void {
 	}
 
 	public function testChildExistsTrue(): void {
+		$comment = $this->createMock(IComment::class);
+		$comment->method('getObjectType')
+			->willReturn('files');
+		$comment->method('getObjectId')
+			->willReturn('19');
+
+		$this->commentsManager->expects($this->once())
+			->method('get')
+			->with('44')
+			->willReturn($comment);
+
 		$this->assertTrue($this->collection->childExists('44'));
 	}
 
diff --git a/lib/private/DB/QueryBuilder/QueryBuilder.php b/lib/private/DB/QueryBuilder/QueryBuilder.php
index c0cbff8d3f523..9c891080f4061 100644
--- a/lib/private/DB/QueryBuilder/QueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/QueryBuilder.php
@@ -1117,6 +1117,10 @@ public function orHaving(...$having) {
 	 * @return $this This QueryBuilder instance.
 	 */
 	public function orderBy($sort, $order = null) {
+		if ($order !== null && !in_array(strtoupper((string) $order), ['ASC', 'DESC'], true)) {
+			$order = null;
+		}
+
 		$this->queryBuilder->orderBy(
 			$this->helper->quoteColumnName($sort),
 			$order
@@ -1134,6 +1138,10 @@ public function orderBy($sort, $order = null) {
 	 * @return $this This QueryBuilder instance.
 	 */
 	public function addOrderBy($sort, $order = null) {
+		if ($order !== null && !in_array(strtoupper((string) $order), ['ASC', 'DESC'], true)) {
+			$order = null;
+		}
+
 		$this->queryBuilder->addOrderBy(
 			$this->helper->quoteColumnName($sort),
 			$order
diff --git a/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php b/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php
index 018b891cd7118..3b7347829d130 100644
--- a/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/Sharded/ShardedQueryBuilder.php
@@ -276,13 +276,21 @@ public function setFirstResult($firstResult) {
 	}
 
 	public function addOrderBy($sort, $order = null) {
-		$this->registerOrder((string) $sort, (string) $order ?? 'ASC');
+		if ($order !== null && !in_array(strtoupper((string) $order), ['ASC', 'DESC'], true)) {
+			$order = null;
+		}
+
+		$this->registerOrder((string) $sort, (string) ($order ?? 'ASC'));
 		return parent::addOrderBy($sort, $order);
 	}
 
 	public function orderBy($sort, $order = null) {
+		if ($order !== null && !in_array(strtoupper((string) $order), ['ASC', 'DESC'], true)) {
+			$order = null;
+		}
+
 		$this->sortList = [];
-		$this->registerOrder((string) $sort, (string) $order ?? 'ASC');
+		$this->registerOrder((string) $sort, (string) ($order ?? 'ASC'));
 		return parent::orderBy($sort, $order);
 	}