diff --git a/src/web-server/shared-routes.ts b/src/web-server/shared-routes.ts
index 4dcf1a5b..507270e5 100644
--- a/src/web-server/shared-routes.ts
+++ b/src/web-server/shared-routes.ts
@@ -13,6 +13,10 @@ import { getClaudeConfigDir } from '../utils/claude-config-path';
 
 export const sharedRoutes = Router();
 
+const MAX_DIRECTORY_TRAVERSAL_DEPTH = 10;
+const MAX_DESCRIPTION_LENGTH = 140;
+const MAX_MARKDOWN_FILE_BYTES = 1024 * 1024; // 1 MiB
+
 interface SharedItem {
   name: string;
   description: string;
@@ -222,16 +226,19 @@ interface MarkdownFileEntry {
 }
 
 function collectMarkdownFiles(sharedDir: string, allowedRoots: Set<string>): MarkdownFileEntry[] {
-  const directoriesToVisit = [sharedDir];
+  const directoriesToVisit: Array<{ path: string; depth: number }> = [
+    { path: sharedDir, depth: 0 },
+  ];
   const visitedDirectories = new Set<string>();
   const markdownFiles: MarkdownFileEntry[] = [];
 
   while (directoriesToVisit.length > 0) {
-    const currentDir = directoriesToVisit.pop();
-    if (!currentDir) {
+    const current = directoriesToVisit.pop();
+    if (!current) {
       continue;
     }
 
+    const currentDir = current.path;
     const resolvedCurrentDir = safeRealPath(currentDir);
     if (!resolvedCurrentDir || !isPathWithinAny(resolvedCurrentDir, allowedRoots)) {
       continue;
@@ -265,7 +272,9 @@ function collectMarkdownFiles(sharedDir: string, allowedRoots: Set<string>): Mar
       }
 
       if (stats.isDirectory()) {
-        directoriesToVisit.push(entryPath);
+        if (current.depth < MAX_DIRECTORY_TRAVERSAL_DEPTH) {
+          directoriesToVisit.push({ path: entryPath, depth: current.depth + 1 });
+        }
         continue;
       }
 
@@ -324,12 +333,11 @@ function stripFrontmatter(content: string): string {
 }
 
 function trimDescription(description: string): string {
-  const maxLength = 140;
-  if (description.length <= maxLength) {
+  if (description.length <= MAX_DESCRIPTION_LENGTH) {
     return description;
   }
 
-  return `${description.slice(0, maxLength - 3).trimEnd()}...`;
+  return `${description.slice(0, MAX_DESCRIPTION_LENGTH - 3).trimEnd()}...`;
 }
 
 function readFirstMarkdownDescription(
@@ -357,6 +365,9 @@ function readMarkdownDescription(markdownPath: string, allowedRoots: Set<string>
     if (!stats.isFile()) {
       return null;
     }
+    if (stats.size > MAX_MARKDOWN_FILE_BYTES) {
+      return null;
+    }
     const content = fs.readFileSync(resolvedMarkdownPath, 'utf8');
     return extractDescription(content);
   } catch {
diff --git a/tests/unit/web-server/shared-routes.test.ts b/tests/unit/web-server/shared-routes.test.ts
index 458bd6f8..7f8dbfd9 100644
--- a/tests/unit/web-server/shared-routes.test.ts
+++ b/tests/unit/web-server/shared-routes.test.ts
@@ -231,6 +231,45 @@ describe('web-server shared-routes', () => {
     ]);
   });
 
+  it('skips markdown files deeper than traversal depth limit', async () => {
+    const commandsDir = path.join(ccsDir, 'shared', 'commands');
+    let currentDir = commandsDir;
+    for (let index = 0; index < 11; index += 1) {
+      currentDir = path.join(currentDir, `depth-${index}`);
+      fs.mkdirSync(currentDir, { recursive: true });
+    }
+    fs.writeFileSync(path.join(currentDir, 'too-deep.md'), 'This should be ignored');
+
+    const payload = await getJson<{ items: Array<{ name: string }> }>(
+      baseUrl,
+      '/api/shared/commands'
+    );
+
+    expect(payload.items).toEqual([]);
+  });
+
+  it('skips oversized markdown files when extracting descriptions', async () => {
+    const commandsDir = path.join(ccsDir, 'shared', 'commands');
+    fs.mkdirSync(commandsDir, { recursive: true });
+
+    const oversizedBody = `# Big\n\n${'x'.repeat(1024 * 1024)}`;
+    fs.writeFileSync(path.join(commandsDir, 'oversized.md'), oversizedBody);
+    fs.writeFileSync(path.join(commandsDir, 'safe.md'), 'Safe command description');
+
+    const payload = await getJson<{
+      items: Array<{ name: string; type: string; description: string; path: string }>;
+    }>(baseUrl, '/api/shared/commands');
+
+    expect(payload.items).toEqual([
+      {
+        name: 'safe',
+        type: 'command',
+        description: 'Safe command description',
+        path: path.join(commandsDir, 'safe.md'),
+      },
+    ]);
+  });
+
   it('ignores markdown files in shared skills root', async () => {
     const sharedSkillsDir = path.join(ccsDir, 'shared', 'skills');
     fs.mkdirSync(sharedSkillsDir, { recursive: true });