diff --git a/package.json b/package.json
index 4494faded4fee..1b57c74bb7b63 100644
--- a/package.json
+++ b/package.json
@@ -125,7 +125,7 @@
     "@elastic/datemath": "5.0.3",
     "@elastic/ebt": "^1.2.1",
     "@elastic/ecs": "^8.11.5",
-    "@elastic/elasticsearch": "9.0.2",
+    "@elastic/elasticsearch": "9.0.3",
     "@elastic/ems-client": "8.6.3",
     "@elastic/eui": "104.0.2",
     "@elastic/eui-amsterdam": "npm:@elastic/eui@104.0.0-amsterdam.0",
diff --git a/src/core/packages/saved-objects/api-server-internal/src/lib/apis/utils/internal_utils.ts b/src/core/packages/saved-objects/api-server-internal/src/lib/apis/utils/internal_utils.ts
index 7380f2a5b0400..80fd9705fceab 100644
--- a/src/core/packages/saved-objects/api-server-internal/src/lib/apis/utils/internal_utils.ts
+++ b/src/core/packages/saved-objects/api-server-internal/src/lib/apis/utils/internal_utils.ts
@@ -38,7 +38,7 @@ export function getBulkOperationError(
   id: string,
   rawResponse: {
     status: number;
-    error?: { type: string; reason?: string; index: string };
+    error?: { type: string; reason?: string | null; index: string };
     // Other fields are present on a bulk operation result but they are irrelevant for this function
   }
 ): Payload | undefined {
diff --git a/src/core/packages/saved-objects/migration-server-internal/src/actions/es_errors.ts b/src/core/packages/saved-objects/migration-server-internal/src/actions/es_errors.ts
index 0ea6ccc227cba..d2c47e40a0fb1 100644
--- a/src/core/packages/saved-objects/migration-server-internal/src/actions/es_errors.ts
+++ b/src/core/packages/saved-objects/migration-server-internal/src/actions/es_errors.ts
@@ -41,7 +41,10 @@ export const isClusterShardLimitExceeded = (errorCause?: ErrorCause): boolean =>
   );
 };
 
-export const hasAllKeywordsInOrder = (message: string | undefined, keywords: string[]): boolean => {
+export const hasAllKeywordsInOrder = (
+  message: string | null | undefined,
+  keywords: string[]
+): boolean => {
   if (!message || !keywords.length) {
     return false;
   }
diff --git a/src/core/packages/saved-objects/migration-server-internal/src/actions/wait_for_task.ts b/src/core/packages/saved-objects/migration-server-internal/src/actions/wait_for_task.ts
index 9fc717e2a5f0e..ca2bb26eb0b21 100644
--- a/src/core/packages/saved-objects/migration-server-internal/src/actions/wait_for_task.ts
+++ b/src/core/packages/saved-objects/migration-server-internal/src/actions/wait_for_task.ts
@@ -20,7 +20,7 @@ import {
 
 /** @internal */
 export interface WaitForTaskResponse {
-  error: Option.Option<{ type: string; reason?: string; index?: string }>;
+  error: Option.Option<{ type: string; reason?: string | null; index?: string }>;
   completed: boolean;
   failures: Option.Option<any[]>;
   description?: string;
diff --git a/src/core/packages/security/server/src/authentication/api_keys/api_keys.ts b/src/core/packages/security/server/src/authentication/api_keys/api_keys.ts
index 56974f5dcf409..07d8c20fd74ed 100644
--- a/src/core/packages/security/server/src/authentication/api_keys/api_keys.ts
+++ b/src/core/packages/security/server/src/authentication/api_keys/api_keys.ts
@@ -203,10 +203,10 @@ export interface InvalidateAPIKeyResult {
    */
   error_details?: Array<{
     type?: string;
-    reason?: string;
+    reason?: string | null;
     caused_by?: {
       type?: string;
-      reason?: string;
+      reason?: string | null;
     };
   }>;
 }
diff --git a/x-pack/platform/packages/shared/ml/error_utils/src/process_errors.ts b/x-pack/platform/packages/shared/ml/error_utils/src/process_errors.ts
index 49d4e81f51a11..a1a4b1006147c 100644
--- a/x-pack/platform/packages/shared/ml/error_utils/src/process_errors.ts
+++ b/x-pack/platform/packages/shared/ml/error_utils/src/process_errors.ts
@@ -75,7 +75,8 @@ export const extractErrorProperties = (error: ErrorType): MLErrorObject => {
       ) {
         errObj.causedBy =
           error.body.attributes.body.error.caused_by?.caused_by?.reason ||
-          error.body.attributes.body.error.caused_by?.reason;
+          error.body.attributes.body.error.caused_by?.reason ||
+          undefined; // Remove 'null' option from the types
       }
       if (
         Array.isArray(error.body.attributes.body.error.root_cause) &&
diff --git a/x-pack/platform/plugins/shared/alerting/server/alert_deletion/lib/delete_alerts_for_query.ts b/x-pack/platform/plugins/shared/alerting/server/alert_deletion/lib/delete_alerts_for_query.ts
index 71aa4425d3986..0ca7b000bbe37 100644
--- a/x-pack/platform/plugins/shared/alerting/server/alert_deletion/lib/delete_alerts_for_query.ts
+++ b/x-pack/platform/plugins/shared/alerting/server/alert_deletion/lib/delete_alerts_for_query.ts
@@ -104,7 +104,7 @@ export const deleteAlertsForQuery = async (
                 action: AlertAuditAction.DELETE,
                 id: alertUuid,
                 outcome: 'failure',
-                error: new Error(item.delete?.error?.reason),
+                error: new Error(item.delete?.error?.reason ?? undefined), // reason can be null and it's not a valid parameter for Error
               })
             );
             errors.push(`Error deleting alert "${alertUuid!}" - ${item.delete?.error?.reason}`);
diff --git a/x-pack/platform/plugins/shared/fleet/server/services/agents/update_agent_tags_action_runner.ts b/x-pack/platform/plugins/shared/fleet/server/services/agents/update_agent_tags_action_runner.ts
index 309aa80f4d8c2..a12e2dcddb05e 100644
--- a/x-pack/platform/plugins/shared/fleet/server/services/agents/update_agent_tags_action_runner.ts
+++ b/x-pack/platform/plugins/shared/fleet/server/services/agents/update_agent_tags_action_runner.ts
@@ -196,7 +196,7 @@ export async function updateTagsBatch(
         agentId: failure.id,
         actionId,
         namespace: spaceId,
-        error: failure.cause.reason,
+        error: failure.cause.reason ?? undefined, // reason can be null and we want to replace it with undefined
       }))
     );
     appContextService.getLogger().debug(`action failed result wrote on ${failureCount} agents`);
diff --git a/x-pack/platform/plugins/shared/fleet/server/services/artifacts/artifacts.ts b/x-pack/platform/plugins/shared/fleet/server/services/artifacts/artifacts.ts
index 936e47a486884..f12ceefa5b5c6 100644
--- a/x-pack/platform/plugins/shared/fleet/server/services/artifacts/artifacts.ts
+++ b/x-pack/platform/plugins/shared/fleet/server/services/artifacts/artifacts.ts
@@ -227,7 +227,7 @@ export const bulkDeleteArtifacts = async (
     if (res.errors) {
       errors = res.items.reduce<Error[]>((acc, item) => {
         if (item.delete?.error) {
-          acc.push(new Error(item.delete.error.reason));
+          acc.push(new Error(item.delete.error.reason ?? undefined)); // reason can be null and it's not a valid parameter for Error
         }
         return acc;
       }, []);
diff --git a/x-pack/platform/plugins/shared/ml/public/application/model_management/test_models/models/inference_base.ts b/x-pack/platform/plugins/shared/ml/public/application/model_management/test_models/models/inference_base.ts
index edcee2f4f9ef1..25ab8ea5c03e2 100644
--- a/x-pack/platform/plugins/shared/ml/public/application/model_management/test_models/models/inference_base.ts
+++ b/x-pack/platform/plugins/shared/ml/public/application/model_management/test_models/models/inference_base.ts
@@ -393,7 +393,7 @@ export abstract class InferenceBase<TInferResponse> {
     if (doc === undefined) {
       if (error) {
         this.setFinishedWithErrors(error as unknown as MLHttpFetchError);
-        throw Error(error.reason);
+        throw Error(error.reason ?? undefined); // reason can be null and it's not a valid parameter for Error
       }
 
       throw Error(
diff --git a/x-pack/platform/plugins/shared/task_manager/server/task_store.ts b/x-pack/platform/plugins/shared/task_manager/server/task_store.ts
index df045724a9a4b..25b7661b18af2 100644
--- a/x-pack/platform/plugins/shared/task_manager/server/task_store.ts
+++ b/x-pack/platform/plugins/shared/task_manager/server/task_store.ts
@@ -634,7 +634,7 @@ export class TaskStore {
 
       if (item.update?.error) {
         const err = new BulkUpdateError({
-          message: item.update.error.reason,
+          message: item.update.error.reason ?? undefined, // reason can be null, and we want to keep `message` as string | undefined
           type: item.update.error.type,
           statusCode: item.update.status,
         });
diff --git a/x-pack/solutions/security/plugins/security_solution/server/lib/detection_engine/rule_types/utils/log_cluster_shard_failures_esql.test.ts b/x-pack/solutions/security/plugins/security_solution/server/lib/detection_engine/rule_types/utils/log_cluster_shard_failures_esql.test.ts
index f4eb8d89229a4..cf7c7a34a0401 100644
--- a/x-pack/solutions/security/plugins/security_solution/server/lib/detection_engine/rule_types/utils/log_cluster_shard_failures_esql.test.ts
+++ b/x-pack/solutions/security/plugins/security_solution/server/lib/detection_engine/rule_types/utils/log_cluster_shard_failures_esql.test.ts
@@ -42,7 +42,7 @@ describe('logClusterShardFailuresEsql', () => {
   it('should add warning message when shard failures exist in a single cluster', () => {
     const shardFailure: EsqlEsqlShardFailure = {
       reason: { type: 'test_failure', reason: 'test failure' },
-      shard: '0',
+      shard: 0,
       index: 'test-index',
     };
 
@@ -70,13 +70,13 @@ describe('logClusterShardFailuresEsql', () => {
   it('should add warning message when shard failures exist in multiple clusters', () => {
     const shardFailure1: EsqlEsqlShardFailure = {
       reason: { type: 'test_failure_1', reason: 'test failure 1' },
-      shard: '0',
+      shard: 0,
       index: 'test-index-1',
     };
 
     const shardFailure2: EsqlEsqlShardFailure = {
       reason: { type: 'test_failure_2', reason: 'test failure 2' },
-      shard: '1',
+      shard: 1,
       index: 'test-index-2',
     };
 
diff --git a/x-pack/solutions/security/plugins/security_solution/server/lib/types.ts b/x-pack/solutions/security/plugins/security_solution/server/lib/types.ts
index 6d20331e770ab..403c0b597073c 100644
--- a/x-pack/solutions/security/plugins/security_solution/server/lib/types.ts
+++ b/x-pack/solutions/security/plugins/security_solution/server/lib/types.ts
@@ -27,12 +27,12 @@ export type ShardError = Partial<{
   node: string;
   reason: Partial<{
     type: string;
-    reason: string;
+    reason: string | null;
     index_uuid: string;
     index: string;
     caused_by: Partial<{
       type: string;
-      reason: string;
+      reason: string | null;
     }>;
   }>;
 }>;
diff --git a/yarn.lock b/yarn.lock
index 5c460502e8b1f..6fff74a738b74 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2139,10 +2139,10 @@
     "@elastic/transport" "^8.3.1"
     tslib "^2.4.0"
 
-"@elastic/elasticsearch@9.0.2":
-  version "9.0.2"
-  resolved "https://registry.yarnpkg.com/@elastic/elasticsearch/-/elasticsearch-9.0.2.tgz#66fb8465fdeabb0c1174d3c48c0a2d5ad5d177c4"
-  integrity sha512-uKA0PuPSND3OhHH9UFqnKZfxifAg/8mQW4VnrQ+sUtusTbPhGuErs5NeWCPyd/RLgruBWBmLSv1zzEv5GS+UnA==
+"@elastic/elasticsearch@9.0.3":
+  version "9.0.3"
+  resolved "https://registry.yarnpkg.com/@elastic/elasticsearch/-/elasticsearch-9.0.3.tgz#96302c6dfae27503d5271aba318883fdef4051bd"
+  integrity sha512-aagnssrVQi538wExO0Au169amtq68sXSwQMyzblQVAsqcmbqRTtzmGhKOjnDP0LK3ml0Mtje1uX+Vda7RhqDsA==
   dependencies:
     "@elastic/transport" "^9.0.1"
     apache-arrow "18.x - 19.x"