diff --git a/packages/angular/build/src/builders/application/tests/options/assets_spec.ts b/packages/angular/build/src/builders/application/tests/options/assets_spec.ts
index 96ae3c0d943e..fad28f5635da 100644
--- a/packages/angular/build/src/builders/application/tests/options/assets_spec.ts
+++ b/packages/angular/build/src/builders/application/tests/options/assets_spec.ts
@@ -359,6 +359,27 @@ describeBuilder(buildApplication, APPLICATION_BUILDER_INFO, (harness) => {
         harness.expectFile('dist/browser/subdirectory/test.svg').content.toBe('<svg></svg>');
       });
 
+      it('fails if asset input option is outside workspace root (relative)', async () => {
+        harness.useTarget('build', {
+          ...BASE_OPTIONS,
+          assets: [{ glob: '**/*', input: '../outside', output: '.' }],
+        });
+
+        const { error } = await harness.executeOnce({ outputLogsOnException: false });
+
+        expect(error?.message).toContain('asset path must be within the workspace root');
+      });
+
+      it('fails if asset input option is outside workspace root (absolute)', async () => {
+        harness.useTarget('build', {
+          ...BASE_OPTIONS,
+          assets: [{ glob: '**/*', input: '/tmp/outside-workspace', output: '.' }],
+        });
+
+        const { error } = await harness.executeOnce({ outputLogsOnException: false });
+
+        expect(error?.message).toContain('asset path must be within the workspace root');
+      });
       it('fails if output option is not within project output path', async () => {
         await harness.writeFile('test.svg', '<svg></svg>');
 
diff --git a/packages/angular/build/src/utils/normalize-asset-patterns.ts b/packages/angular/build/src/utils/normalize-asset-patterns.ts
index 8a8b2c2cbf1f..396d789f8634 100644
--- a/packages/angular/build/src/utils/normalize-asset-patterns.ts
+++ b/packages/angular/build/src/utils/normalize-asset-patterns.ts
@@ -10,6 +10,7 @@ import assert from 'node:assert';
 import { statSync } from 'node:fs';
 import * as path from 'node:path';
 import { AssetPattern, AssetPatternClass } from '../builders/application/schema';
+import { isSubDirectory } from './path';
 
 export class MissingAssetSourceRootException extends Error {
   constructor(path: string) {
@@ -68,6 +69,10 @@ export function normalizeAssetPatterns(
 
       assetPattern = { glob, input, output };
     } else {
+      if (!isSubDirectory(workspaceRoot, assetPattern.input)) {
+        throw new Error(`The ${assetPattern.input} asset path must be within the workspace root.`);
+      }
+
       assetPattern.output = path.join('.', assetPattern.output ?? '');
     }
 
diff --git a/packages/angular/build/src/utils/path.ts b/packages/angular/build/src/utils/path.ts
index 036dcb23502e..eafef4ee9f2b 100644
--- a/packages/angular/build/src/utils/path.ts
+++ b/packages/angular/build/src/utils/path.ts
@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import { posix } from 'node:path';
+import { normalize, posix, resolve } from 'node:path';
 import { platform } from 'node:process';
 
 const WINDOWS_PATH_SEPERATOR_REGEXP = /\\/g;
@@ -35,3 +35,17 @@ const WINDOWS_PATH_SEPERATOR_REGEXP = /\\/g;
 export function toPosixPath(path: string): string {
   return platform === 'win32' ? path.replace(WINDOWS_PATH_SEPERATOR_REGEXP, posix.sep) : path;
 }
+
+/**
+ * Determines if a path is a subdirectory or file within a parent directory.
+ *
+ * @param parent - The parent directory path.
+ * @param child - The child path to check.
+ * @returns `true` if the child path is within the parent directory, `false` otherwise.
+ */
+export function isSubDirectory(parent: string, child: string): boolean {
+  const normalizedParent = normalize(parent);
+  const resolvedChild = resolve(parent, child);
+
+  return resolvedChild.startsWith(normalizedParent);
+}
diff --git a/packages/angular/build/src/utils/resolve-assets.ts b/packages/angular/build/src/utils/resolve-assets.ts
index e98879e58de7..71b1c0e4768b 100644
--- a/packages/angular/build/src/utils/resolve-assets.ts
+++ b/packages/angular/build/src/utils/resolve-assets.ts
@@ -8,6 +8,7 @@
 
 import path from 'node:path';
 import { glob } from 'tinyglobby';
+import { isSubDirectory } from './path';
 
 export async function resolveAssets(
   entries: {
@@ -25,7 +26,12 @@ export async function resolveAssets(
   const outputFiles: { source: string; destination: string }[] = [];
 
   for (const entry of entries) {
+    if (!isSubDirectory(root, entry.input)) {
+      throw new Error(`The ${entry.input} asset path must be within the workspace root.`);
+    }
+
     const cwd = path.resolve(root, entry.input);
+
     const files = await glob(entry.glob, {
       cwd,
       dot: true,
diff --git a/packages/angular_devkit/build_angular/src/builders/browser/tests/options/assets_spec.ts b/packages/angular_devkit/build_angular/src/builders/browser/tests/options/assets_spec.ts
index b8752e7c275e..c7ac266cf036 100644
--- a/packages/angular_devkit/build_angular/src/builders/browser/tests/options/assets_spec.ts
+++ b/packages/angular_devkit/build_angular/src/builders/browser/tests/options/assets_spec.ts
@@ -359,6 +359,28 @@ describeBuilder(buildWebpackBrowser, BROWSER_BUILDER_INFO, (harness) => {
         harness.expectFile('dist/subdirectory/test.svg').content.toBe('<svg></svg>');
       });
 
+      it('fails if asset input option is outside workspace root (relative)', async () => {
+        harness.useTarget('build', {
+          ...BASE_OPTIONS,
+          assets: [{ glob: '**/*', input: '../outside', output: '.' }],
+        });
+
+        const { result } = await harness.executeOnce();
+
+        expect(result?.error).toMatch('asset path must be within the workspace root');
+      });
+
+      it('fails if asset input option is outside workspace root (absolute)', async () => {
+        harness.useTarget('build', {
+          ...BASE_OPTIONS,
+          assets: [{ glob: '**/*', input: '/tmp/outside-workspace', output: '.' }],
+        });
+
+        const { result } = await harness.executeOnce();
+
+        expect(result?.error).toMatch('asset path must be within the workspace root');
+      });
+
       it('fails if output option is not within project output path', async () => {
         await harness.writeFile('test.svg', '<svg></svg>');
 
diff --git a/packages/angular_devkit/build_angular/src/utils/normalize-asset-patterns.ts b/packages/angular_devkit/build_angular/src/utils/normalize-asset-patterns.ts
index ef421d81042c..20e97e1d5162 100644
--- a/packages/angular_devkit/build_angular/src/utils/normalize-asset-patterns.ts
+++ b/packages/angular_devkit/build_angular/src/utils/normalize-asset-patterns.ts
@@ -43,7 +43,7 @@ export function normalizeAssetPatterns(
       }
 
       let glob: string, input: string;
-      let isDirectory = false;
+      let isDirectory: boolean;
 
       try {
         isDirectory = statSync(resolvedAssetPath).isDirectory();
@@ -68,6 +68,11 @@ export function normalizeAssetPatterns(
 
       assetPattern = { glob, input, output };
     } else {
+      const resolvedInput = path.resolve(workspaceRoot, assetPattern.input);
+      if (!resolvedInput.startsWith(workspaceRoot)) {
+        throw new Error(`The ${assetPattern.input} asset path must be within the workspace root.`);
+      }
+
       assetPattern.output = path.join('.', assetPattern.output ?? '');
     }
 
diff --git a/tests/legacy-cli/e2e/tests/commands/serve/assets.ts b/tests/legacy-cli/e2e/tests/commands/serve/assets.ts
index 83fcb42aa8f2..3ddd7f8b74b1 100644
--- a/tests/legacy-cli/e2e/tests/commands/serve/assets.ts
+++ b/tests/legacy-cli/e2e/tests/commands/serve/assets.ts
@@ -1,59 +1,30 @@
 import assert from 'node:assert';
-import { randomUUID } from 'node:crypto';
-import { mkdir, rm, writeFile } from 'node:fs/promises';
-import { ngServe, updateJsonFile } from '../../../utils/project';
+import { ngServe } from '../../../utils/project';
 import { getGlobalVariable } from '../../../utils/env';
 
 export default async function () {
-  const outsideDirectoryName = `../outside-${randomUUID()}`;
+  const port = await ngServe();
+  let response = await fetch(`http://localhost:${port}/favicon.ico`);
+  assert.strictEqual(response.status, 200, 'favicon.ico response should be ok');
 
-  await updateJsonFile('angular.json', (json) => {
-    // Ensure assets located outside the workspace root work with the dev server
-    json.projects['test-project'].architect.build.options.assets.push({
-      'input': outsideDirectoryName,
-      'glob': '**/*',
-      'output': './outside',
-    });
+  // A non-existent HTML file request with accept header should fallback to the index HTML
+  response = await fetch(`http://localhost:${port}/does-not-exist.html`, {
+    headers: { accept: 'text/html' },
   });
-
-  await mkdir(outsideDirectoryName);
-  try {
-    await writeFile(`${outsideDirectoryName}/some-asset.xyz`, 'XYZ');
-
-    const port = await ngServe();
-
-    let response = await fetch(`http://localhost:${port}/favicon.ico`);
-    assert.strictEqual(response.status, 200, 'favicon.ico response should be ok');
-
-    response = await fetch(`http://localhost:${port}/outside/some-asset.xyz`);
-    assert.strictEqual(response.status, 200, 'outside/some-asset.xyz response should be ok');
-    assert.strictEqual(await response.text(), 'XYZ', 'outside/some-asset.xyz content is wrong');
-
-    // A non-existent HTML file request with accept header should fallback to the index HTML
-    response = await fetch(`http://localhost:${port}/does-not-exist.html`, {
-      headers: { accept: 'text/html' },
-    });
-    assert.strictEqual(
-      response.status,
-      200,
-      'non-existent file response should fallback and be ok',
-    );
-    assert.match(
-      await response.text(),
-      /<app-root/,
-      'non-existent file response should fallback and contain html',
-    );
-
-    // Vite will incorrectly fallback in all non-existent cases so skip last test case
-    // TODO: Remove conditional when Vite handles this case
-    if (getGlobalVariable('argv')['esbuild']) {
-      return;
-    }
-
-    // A non-existent file without an html accept header should not be found.
-    response = await fetch(`http://localhost:${port}/does-not-exist.png`);
-    assert.strictEqual(response.status, 404, 'non-existent file response should be not found');
-  } finally {
-    await rm(outsideDirectoryName, { force: true, recursive: true });
+  assert.strictEqual(response.status, 200, 'non-existent file response should fallback and be ok');
+  assert.match(
+    await response.text(),
+    /<app-root/,
+    'non-existent file response should fallback and contain html',
+  );
+
+  // Vite will incorrectly fallback in all non-existent cases  so skip last test case
+  // TODO: Remove conditional when Vite handles this case
+  if (getGlobalVariable('argv')['esbuild']) {
+    return;
   }
+
+  // A non-existent file without an html accept header should not be found.
+  response = await fetch(`http://localhost:${port}/does-not-exist.png`);
+  assert.strictEqual(response.status, 404, 'non-existent file response should be not found');
 }