From 929b388ba5df98487382e60f3a2c2a839903f4c1 Mon Sep 17 00:00:00 2001
From: Nikolay Benlioglu <36928407+nbenliogludev@users.noreply.github.com>
Date: Fri, 27 Sep 2024 18:14:51 +0300
Subject: [PATCH] fix: handle null path parameter in
 RestNodesCapabilitiesAction (#113413)

---
 docs/changelog/113413.yaml                                  | 6 ++++++
 .../action/admin/cluster/RestNodesCapabilitiesAction.java   | 5 ++++-
 2 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 docs/changelog/113413.yaml

diff --git a/docs/changelog/113413.yaml b/docs/changelog/113413.yaml
new file mode 100644
index 0000000000000..8b1104ba61fe4
--- /dev/null
+++ b/docs/changelog/113413.yaml
@@ -0,0 +1,6 @@
+pr: 113413
+summary: Fixed a `NullPointerException` in `_capabilities` API when the `path` parameter is null.
+area: Infra/REST API
+type: bug
+issues:
+  - 113413
diff --git a/server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestNodesCapabilitiesAction.java b/server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestNodesCapabilitiesAction.java
index ad405656631b0..5c8e5928678c3 100644
--- a/server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestNodesCapabilitiesAction.java
+++ b/server/src/main/java/org/elasticsearch/rest/action/admin/cluster/RestNodesCapabilitiesAction.java
@@ -54,9 +54,12 @@ protected RestChannelConsumer prepareRequest(RestRequest request, NodeClient cli
             ? new NodesCapabilitiesRequest(client.getLocalNodeId())
             : new NodesCapabilitiesRequest();
 
+        // Handle the 'path' parameter, use "/" as default if not provided
+        String path = URLDecoder.decode(request.param("path", "/"), StandardCharsets.UTF_8);
+
         NodesCapabilitiesRequest r = requestNodes.timeout(getTimeout(request))
             .method(RestRequest.Method.valueOf(request.param("method", "GET")))
-            .path(URLDecoder.decode(request.param("path"), StandardCharsets.UTF_8))
+            .path(path)
             .parameters(request.paramAsStringArray("parameters", Strings.EMPTY_ARRAY))
             .capabilities(request.paramAsStringArray("capabilities", Strings.EMPTY_ARRAY))
             .restApiVersion(request.getRestApiVersion());