diff --git a/src/assets/__tests__/__snapshots__/dockerfile-render.test.ts.snap b/src/assets/__tests__/__snapshots__/dockerfile-render.test.ts.snap
index 4bc6e9294..90bb1457d 100644
--- a/src/assets/__tests__/__snapshots__/dockerfile-render.test.ts.snap
+++ b/src/assets/__tests__/__snapshots__/dockerfile-render.test.ts.snap
@@ -1,7 +1,7 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
 exports[`Dockerfile enableOtel rendering > renders opentelemetry-instrument CMD when enableOtel is true > Dockerfile-enableOtel-true 1`] = `
-"FROM public.ecr.aws/docker/library/python:3.12-slim-bookworm
+"FROM public.ecr.aws/docker/library/python:3.12-slim-trixie
 
 RUN pip install --no-cache-dir uv
 
@@ -41,7 +41,7 @@ CMD ["opentelemetry-instrument", "python", "-m", "main"]
 `;
 
 exports[`Dockerfile enableOtel rendering > renders plain python CMD when enableOtel is false > Dockerfile-enableOtel-false 1`] = `
-"FROM public.ecr.aws/docker/library/python:3.12-slim-bookworm
+"FROM public.ecr.aws/docker/library/python:3.12-slim-trixie
 
 RUN pip install --no-cache-dir uv
 
diff --git a/src/assets/container/python/Dockerfile b/src/assets/container/python/Dockerfile
index 60a0e87fc..cb3569eff 100644
--- a/src/assets/container/python/Dockerfile
+++ b/src/assets/container/python/Dockerfile
@@ -1,4 +1,4 @@
-FROM public.ecr.aws/docker/library/python:3.12-slim-bookworm
+FROM public.ecr.aws/docker/library/python:3.12-slim-trixie
 
 RUN pip install --no-cache-dir uv
 
diff --git a/src/cli/commands/import/actions.ts b/src/cli/commands/import/actions.ts
index 990fe006f..f8fac62fb 100644
--- a/src/cli/commands/import/actions.ts
+++ b/src/cli/commands/import/actions.ts
@@ -9,6 +9,7 @@ import type {
 } from '../../../schema';
 import { validateAwsCredentials } from '../../aws/account';
 import { arnPrefix } from '../../aws/partition';
+import { PYTHON_BASE_IMAGE } from '../../constants';
 import { ExecLogger } from '../../logging';
 import { setupPythonProject } from '../../operations/python/setup';
 import { executeCdkImportPipeline } from './import-pipeline';
@@ -383,7 +384,7 @@ export async function handleImport(options: ImportOptions): Promise<ImportResult
               fs.writeFileSync(
                 destDockerfile,
                 [
-                  'FROM public.ecr.aws/docker/library/python:3.12-slim-bookworm',
+                  `FROM ${PYTHON_BASE_IMAGE}`,
                   'RUN pip install --no-cache-dir uv',
                   'WORKDIR /app',
                   '',
diff --git a/src/cli/constants.ts b/src/cli/constants.ts
index 85d053817..ecb60c2c8 100644
--- a/src/cli/constants.ts
+++ b/src/cli/constants.ts
@@ -68,3 +68,8 @@ export const SCHEMA_VERSION = 1;
  * Default runtime endpoint name used in log group paths and console URLs.
  */
 export const DEFAULT_ENDPOINT_NAME = 'DEFAULT';
+
+/**
+ * Base image for generated Python Dockerfiles.
+ */
+export const PYTHON_BASE_IMAGE = 'public.ecr.aws/docker/library/python:3.12-slim-trixie';
diff --git a/src/cli/operations/deploy/__tests__/preflight-container.test.ts b/src/cli/operations/deploy/__tests__/preflight-container.test.ts
index 0bf4a7af7..ff5f5c3c9 100644
--- a/src/cli/operations/deploy/__tests__/preflight-container.test.ts
+++ b/src/cli/operations/deploy/__tests__/preflight-container.test.ts
@@ -1,10 +1,11 @@
 import type { AgentCoreProjectSpec, DirectoryPath } from '../../../../schema';
 import { validateContainerAgents } from '../preflight.js';
-import { existsSync } from 'node:fs';
+import { existsSync, readFileSync } from 'node:fs';
 import { afterEach, describe, expect, it, vi } from 'vitest';
 
 vi.mock('node:fs', () => ({
   existsSync: vi.fn(),
+  readFileSync: vi.fn(),
 }));
 
 vi.mock('../../../../lib', () => ({
@@ -26,6 +27,7 @@ vi.mock('../../../../lib', () => ({
 }));
 
 const mockedExistsSync = vi.mocked(existsSync);
+const mockedReadFileSync = vi.mocked(readFileSync);
 
 const CONFIG_ROOT = '/project/agentcore';
 
@@ -44,6 +46,11 @@ describe('validateContainerAgents', () => {
     vi.clearAllMocks();
   });
 
+  // Default readFileSync to return a safe Dockerfile so the warning check doesn't fail on unrelated tests
+  function mockValidDockerfile(): void {
+    mockedReadFileSync.mockReturnValue('FROM public.ecr.aws/docker/library/python:3.12-slim-trixie\n');
+  }
+
   it('does nothing when there are no Container agents', () => {
     const spec = makeSpec([{ name: 'zip-agent', build: 'CodeZip', codeLocation: dir('agents/zip-agent') }]);
 
@@ -53,6 +60,7 @@ describe('validateContainerAgents', () => {
 
   it('does nothing when Container agent has a valid Dockerfile', () => {
     mockedExistsSync.mockReturnValue(true);
+    mockValidDockerfile();
 
     const spec = makeSpec([
       { name: 'container-agent', build: 'Container', codeLocation: dir('agents/container-agent') },
@@ -72,6 +80,7 @@ describe('validateContainerAgents', () => {
 
   it('only validates Container agents and skips CodeZip agents', () => {
     mockedExistsSync.mockReturnValue(true);
+    mockValidDockerfile();
 
     const spec = makeSpec([
       { name: 'zip-agent', build: 'CodeZip', codeLocation: dir('agents/zip-agent') },
@@ -104,6 +113,7 @@ describe('validateContainerAgents', () => {
 
   it('checks for custom dockerfile name when specified', () => {
     mockedExistsSync.mockReturnValue(true);
+    mockValidDockerfile();
 
     const spec = makeSpec([
       { name: 'gpu-agent', build: 'Container', codeLocation: dir('agents/gpu'), dockerfile: 'Dockerfile.gpu' },
@@ -124,4 +134,50 @@ describe('validateContainerAgents', () => {
 
     expect(() => validateContainerAgents(spec, CONFIG_ROOT)).toThrow(/Dockerfile\.gpu not found/);
   });
+
+  it('warns when Dockerfile uses deprecated bookworm base image', () => {
+    mockedExistsSync.mockReturnValue(true);
+    mockedReadFileSync.mockReturnValue(
+      'FROM public.ecr.aws/docker/library/python:3.12-slim-bookworm\nRUN pip install uv'
+    );
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => undefined);
+
+    const spec = makeSpec([{ name: 'my-agent', build: 'Container', codeLocation: dir('agents/my-agent') }]);
+
+    expect(() => validateContainerAgents(spec, CONFIG_ROOT)).not.toThrow();
+    expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining('CVE-2026-42010'));
+    expect(warnSpy).toHaveBeenCalledWith(expect.stringContaining('my-agent'));
+
+    warnSpy.mockRestore();
+  });
+
+  it('does not warn when Dockerfile uses trixie base image', () => {
+    mockedExistsSync.mockReturnValue(true);
+    mockedReadFileSync.mockReturnValue(
+      'FROM public.ecr.aws/docker/library/python:3.12-slim-trixie\nRUN pip install uv'
+    );
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => undefined);
+
+    const spec = makeSpec([{ name: 'my-agent', build: 'Container', codeLocation: dir('agents/my-agent') }]);
+
+    expect(() => validateContainerAgents(spec, CONFIG_ROOT)).not.toThrow();
+    expect(warnSpy).not.toHaveBeenCalled();
+
+    warnSpy.mockRestore();
+  });
+
+  it('does not warn when bookworm appears in a non-FROM line', () => {
+    mockedExistsSync.mockReturnValue(true);
+    mockedReadFileSync.mockReturnValue(
+      'FROM public.ecr.aws/docker/library/python:3.12-slim-trixie\n# migrated from slim-bookworm\nRUN pip install uv'
+    );
+    const warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => undefined);
+
+    const spec = makeSpec([{ name: 'my-agent', build: 'Container', codeLocation: dir('agents/my-agent') }]);
+
+    expect(() => validateContainerAgents(spec, CONFIG_ROOT)).not.toThrow();
+    expect(warnSpy).not.toHaveBeenCalled();
+
+    warnSpy.mockRestore();
+  });
 });
diff --git a/src/cli/operations/deploy/preflight.ts b/src/cli/operations/deploy/preflight.ts
index 6577eb529..0c004002d 100644
--- a/src/cli/operations/deploy/preflight.ts
+++ b/src/cli/operations/deploy/preflight.ts
@@ -6,7 +6,7 @@ import { CdkToolkitWrapper, createCdkToolkitWrapper, silentIoHost } from '../../
 import { checkBootstrapStatus, checkStacksStatus, formatCdkEnvironment } from '../../cloudformation';
 import { cleanupStaleLockFiles } from '../../tui/utils';
 import type { IIoHost } from '@aws-cdk/toolkit-lib';
-import { existsSync } from 'node:fs';
+import { existsSync, readFileSync } from 'node:fs';
 import * as path from 'node:path';
 
 export interface PreflightContext {
@@ -198,6 +198,8 @@ export function validateContainerAgents(projectSpec: AgentCoreProjectSpec, confi
         errors.push(
           `Agent "${agent.name}": ${agent.dockerfile ?? DOCKERFILE_NAME} not found at ${dockerfilePath}. Container agents require a Dockerfile.`
         );
+      } else {
+        warnDeprecatedBaseImage(dockerfilePath, agent.name);
       }
     }
   }
@@ -206,6 +208,27 @@ export function validateContainerAgents(projectSpec: AgentCoreProjectSpec, confi
   }
 }
 
+const DEPRECATED_BASE_IMAGES = ['slim-bookworm'];
+
+function warnDeprecatedBaseImage(dockerfilePath: string, agentName: string): void {
+  try {
+    const content = readFileSync(dockerfilePath, 'utf-8');
+    for (const line of content.split('\n')) {
+      if (!/^\s*FROM\s+/i.test(line)) continue;
+      for (const image of DEPRECATED_BASE_IMAGES) {
+        if (line.includes(image)) {
+          console.warn(
+            `Warning: Agent "${agentName}" Dockerfile uses a base image containing "${image}" which is affected by ` +
+              `CVE-2026-42010 (GnuTLS authentication bypass). Update the FROM line to use a Trixie-based variant.`
+          );
+        }
+      }
+    }
+  } catch {
+    // Non-fatal — if we can't read the file, the existing validation will handle it
+  }
+}
+
 /**
  * Builds the CDK project.
  */