diff --git a/actions/setup/js/close_entity_helpers.cjs b/actions/setup/js/close_entity_helpers.cjs
index 439c11dfe0f..213cd4f94b1 100644
--- a/actions/setup/js/close_entity_helpers.cjs
+++ b/actions/setup/js/close_entity_helpers.cjs
@@ -10,6 +10,7 @@ const { sanitizeContent } = require("./sanitize_content.cjs");
 const { buildWorkflowRunUrl } = require("./workflow_metadata_helpers.cjs");
 const { isStagedMode } = require("./safe_output_helpers.cjs");
 const { logStagedPreviewInfo } = require("./staged_preview.cjs");
+const { validateTargetRepo, resolveTargetRepoConfig } = require("./repo_helpers.cjs");
 
 /**
  * @typedef {'issue' | 'pull_request'} EntityType
@@ -262,6 +263,7 @@ function createCloseEntityHandler(config, entityConfig, callbacks, githubClient)
   const maxCount = config.max || 10;
   const comment = config.comment || "";
   const isStaged = isStagedMode(config);
+  const { defaultTargetRepo, allowedRepos } = resolveTargetRepoConfig(config);
 
   let processedCount = 0;
 
@@ -318,6 +320,14 @@ function createCloseEntityHandler(config, entityConfig, callbacks, githubClient)
       core.info(`Target repository: ${entityRepo}`);
     }
 
+    // 4b. Cross-repository allowlist validation (SEC-005)
+    const resolvedRepo = `${owner}/${repoName}`;
+    const repoValidation = validateTargetRepo(resolvedRepo, defaultTargetRepo, allowedRepos);
+    if (!repoValidation.valid) {
+      core.warning(`Skipping ${entityConfig.itemType}: cross-repo check failed for "${resolvedRepo}": ${repoValidation.error}`);
+      return { success: false, error: repoValidation.error };
+    }
+
     try {
       // 5. Entity details fetch
       core.info(`Fetching ${entityConfig.displayName} details for #${entityNumber} in ${owner}/${repoName}`);
diff --git a/actions/setup/js/close_entity_helpers.test.cjs b/actions/setup/js/close_entity_helpers.test.cjs
index 55e1f1ab1c1..f97439fdeb4 100644
--- a/actions/setup/js/close_entity_helpers.test.cjs
+++ b/actions/setup/js/close_entity_helpers.test.cjs
@@ -4,7 +4,7 @@ import path from "path";
 const mockCore = { debug: vi.fn(), info: vi.fn(), warning: vi.fn(), error: vi.fn(), setFailed: vi.fn(), setOutput: vi.fn(), summary: { addRaw: vi.fn().mockReturnThis(), write: vi.fn().mockResolvedValue() } },
   mockContext = { eventName: "issues", runId: 12345, repo: { owner: "testowner", repo: "testrepo" }, payload: { issue: { number: 42 }, pull_request: { number: 100 }, repository: { html_url: "https://github.com/testowner/testrepo" } } };
 ((global.core = mockCore), (global.context = mockContext));
-const { checkLabelFilter, checkTitlePrefixFilter, parseEntityConfig, resolveEntityNumber, escapeMarkdownTitle, ISSUE_CONFIG, PULL_REQUEST_CONFIG } = require("./close_entity_helpers.cjs");
+const { checkLabelFilter, checkTitlePrefixFilter, parseEntityConfig, resolveEntityNumber, escapeMarkdownTitle, createCloseEntityHandler, ISSUE_CONFIG, PULL_REQUEST_CONFIG } = require("./close_entity_helpers.cjs");
 describe("close_entity_helpers", () => {
   (beforeEach(() => {
     (vi.clearAllMocks(),
@@ -237,5 +237,54 @@ describe("close_entity_helpers", () => {
         // System marker should still be present
         expect(withMarker).toContain("<!-- gh-aw-workflow-id: test -->");
       });
+    }),
+    describe("createCloseEntityHandler cross-repo validation", () => {
+      const makeCallbacks = resolveTarget => ({
+        resolveTarget,
+        getDetails: vi.fn().mockResolvedValue({ number: 1, title: "t", labels: [], html_url: "u", state: "open" }),
+        validateLabels: () => ({ valid: true }),
+        buildCommentBody: body => body,
+        addComment: vi.fn().mockResolvedValue({ id: 1, html_url: "u" }),
+        closeEntity: vi.fn().mockResolvedValue({ number: 1, html_url: "u", title: "t" }),
+        buildSuccessResult: (entity, comment, wasClosed, commentPosted) => ({ success: true }),
+      });
+
+      it("should reject cross-repo target not in allowlist", async () => {
+        const config = { "target-repo": "testowner/testrepo", comment: "closing" };
+        const handler = createCloseEntityHandler(
+          config,
+          ISSUE_CONFIG,
+          makeCallbacks(() => ({ success: true, entityNumber: 1, owner: "other-org", repo: "other-repo" })),
+          {}
+        );
+        const result = await handler({ body: "test", type: "close_issue" });
+        expect(result.success).toBe(false);
+        expect(result.error).toContain("not in the allowed-repos list");
+        expect(mockCore.warning).toHaveBeenCalled();
+      });
+
+      it("should allow same-repo target", async () => {
+        const config = { "target-repo": "testowner/testrepo", comment: "closing" };
+        const handler = createCloseEntityHandler(
+          config,
+          ISSUE_CONFIG,
+          makeCallbacks(() => ({ success: true, entityNumber: 1, owner: "testowner", repo: "testrepo" })),
+          {}
+        );
+        const result = await handler({ body: "test", type: "close_issue" });
+        expect(result.success).toBe(true);
+      });
+
+      it("should allow cross-repo target when in allowlist", async () => {
+        const config = { "target-repo": "testowner/testrepo", allowed_repos: ["other-org/other-repo"], comment: "closing" };
+        const handler = createCloseEntityHandler(
+          config,
+          ISSUE_CONFIG,
+          makeCallbacks(() => ({ success: true, entityNumber: 1, owner: "other-org", repo: "other-repo" })),
+          {}
+        );
+        const result = await handler({ body: "test", type: "close_issue" });
+        expect(result.success).toBe(true);
+      });
     }));
 });