diff --git a/packages/blueprints/blueprint/src/resynthesis/merge-strategies/deserialize-strategies.ts b/packages/blueprints/blueprint/src/resynthesis/merge-strategies/deserialize-strategies.ts
index 2f72948e3..d6c88ffe0 100644
--- a/packages/blueprints/blueprint/src/resynthesis/merge-strategies/deserialize-strategies.ts
+++ b/packages/blueprints/blueprint/src/resynthesis/merge-strategies/deserialize-strategies.ts
@@ -10,6 +10,8 @@ import { walkFiles } from '../walk-files';
 export type StrategyLocations = { [bundlePath: string]: Strategy[] };
 export const LOCAL_STRATEGY_ID = 'local';
 
+const ALLOWED_LOCAL_CMD = /^[a-zA-Z0-9._/\-]+((\s+(%[AOBLP]|\S+))+)?$/;
+
 const getStrategyIds = (strategies: StrategyLocations): { [identifier: string]: Strategy } => {
   const ids: { [id: string]: Strategy } = {};
   for (const strategyList of Object.values(strategies)) {
@@ -47,6 +49,13 @@ export const deserializeStrategies = (existingBundle: string, strategyMatch: Str
           });
         }
 
+        if (!ALLOWED_LOCAL_CMD.test(deserializedStrategy.owner)) {
+          throw new BlueprintSynthesisError({
+            message: `Rejected unsafe local merge strategy command: ${deserializedStrategy.owner}`,
+            type: BlueprintSynthesisErrorTypes.ValidationError,
+          });
+        }
+
         deserializedStrategy.strategy = constructLocalStrategy(deserializedStrategy.owner, ownershipPath);
         relevantStrategies.push(deserializedStrategy);
       } else if (deserializedStrategy.identifier in inMemStrategies) {
diff --git a/packages/blueprints/blueprint/src/resynthesis/merge-strategies/local.ts b/packages/blueprints/blueprint/src/resynthesis/merge-strategies/local.ts
index bc8b0bd78..efaabd148 100644
--- a/packages/blueprints/blueprint/src/resynthesis/merge-strategies/local.ts
+++ b/packages/blueprints/blueprint/src/resynthesis/merge-strategies/local.ts
@@ -1,4 +1,4 @@
-import { execSync } from 'child_process';
+import { execFileSync } from 'child_process';
 import { randomBytes } from 'crypto';
 import { mkdirSync, readFileSync, rmSync, writeFileSync } from 'fs';
 import * as path from 'path';
@@ -47,14 +47,14 @@ function runLocalCommand(
 ): Buffer | undefined {
   createTempDir();
 
-  let cmd: string | undefined;
+  let cmdArgs: string[] | undefined;
   try {
     const commonTempFile = createTempFile(buffers.o);
     const existingTempFile = createTempFile(buffers.a);
     const proposedTempFile = createTempFile(buffers.b);
 
     const cwd = path.dirname(ownershipPath);
-    cmd = formatLocalCommand(
+    cmdArgs = formatLocalCommandArgs(
       owner,
       path.relative(cwd, existingTempFile),
       path.relative(cwd, commonTempFile),
@@ -62,7 +62,8 @@ function runLocalCommand(
       resolvedPath,
     );
 
-    execSync(cmd, {
+    const [executable, ...args] = cmdArgs;
+    execFileSync(executable, args, {
       cwd,
     });
 
@@ -70,8 +71,8 @@ function runLocalCommand(
     return getResolvedFile(existingTempFile);
   } catch (error: unknown) {
     let message = 'Failed to run local merge strategy';
-    if (cmd) {
-      message += `: ${cmd}`;
+    if (cmdArgs) {
+      message += `: ${cmdArgs.join(' ')}`;
     }
 
     throw new Error(`${message}: ${error}`);
@@ -118,12 +119,13 @@ function createTempFile(contents: Buffer): string {
   return tempPath;
 }
 
-function formatLocalCommand(commandPattern: string, aPath: string, oPath: string, bPath: string, resolvedPath: string): string {
+function formatLocalCommandArgs(commandPattern: string, aPath: string, oPath: string, bPath: string, resolvedPath: string): string[] {
   // see: https://git-scm.com/docs/gitattributes#_defining_a_custom_merge_driver
-  return commandPattern
+  const substituted = commandPattern
     .replace(/%O/g, oPath)
     .replace(/%A/g, aPath)
     .replace(/%B/g, bPath)
     .replace(/%P/g, resolvedPath)
     .replace(/%L/g, `${CONFLICT_MARKER_LENGTH}`);
+  return substituted.split(/\s+/).filter(s => s.length > 0);
 }
diff --git a/packages/blueprints/sam-serverless-app/src/blueprint.ts b/packages/blueprints/sam-serverless-app/src/blueprint.ts
index 27aac3eb6..da563ba35 100644
--- a/packages/blueprints/sam-serverless-app/src/blueprint.ts
+++ b/packages/blueprints/sam-serverless-app/src/blueprint.ts
@@ -261,7 +261,7 @@ export class Blueprint extends ParentBlueprint {
 
     super.synth();
 
-    cp.execSync(`rm -rf ${toDeletePath}`);
+    fs.rmSync(toDeletePath, { recursive: true, force: true });
 
     // update permissions
     const permissionChangeContext: FileTemplateContext = {
@@ -392,12 +392,10 @@ export class Blueprint extends ParentBlueprint {
     //   `${sourceDir}`,
     // ]);
 
-    const assetPath = path.join('static-assets', 'sam-templates', params.runtime, params.gitSrcPath, '{{cookiecutter.project_name}}', '*');
+    const assetDir = path.join('static-assets', 'sam-templates', params.runtime, params.gitSrcPath, '{{cookiecutter.project_name}}');
 
     //TODO: this is a temporary fix to work around SVN failures.  These assets need to be updated.
-    cp.execSync(`cp -R ./${assetPath} ${sourceDir}/`, {
-      cwd: process.cwd(),
-    });
+    fs.cpSync(path.resolve(process.cwd(), assetDir), sourceDir, { recursive: true });
 
     cp.execFileSync('rm', ['-rf', `${sourceDir}/.svn`, `${sourceDir}/.gitignore`, `${sourceDir}/README.md`, `${sourceDir}/template.yaml`]);
 
diff --git a/packages/utils/blueprint-cli/src/bundle/package-bundle.ts b/packages/utils/blueprint-cli/src/bundle/package-bundle.ts
index 6ca685da1..2f07790c1 100644
--- a/packages/utils/blueprint-cli/src/bundle/package-bundle.ts
+++ b/packages/utils/blueprint-cli/src/bundle/package-bundle.ts
@@ -14,13 +14,13 @@ export function packageBundle(
   },
 ) {
   try {
-    let zipCommand = [`zip ${path.basename(outputPathAbs)}`, `-r ${path.basename(folderPathAbs)}`, '-x **/.git/**'].join(' ');
-    logger.debug(zipCommand);
+    const zipArgs = [path.basename(outputPathAbs), '-r', path.basename(folderPathAbs), '-x', '**/.git/**'];
     if (options.encrypt) {
       logger.info('Packing folder. Enter zip password ...');
-      zipCommand = `${zipCommand} -e`;
+      zipArgs.push('-e');
     }
-    cp.execSync(zipCommand, {
+    logger.debug(`zip ${zipArgs.join(' ')}`);
+    cp.execFileSync('zip', zipArgs, {
       stdio: 'inherit',
       cwd: path.dirname(folderPathAbs),
     });
diff --git a/packages/utils/blueprint-cli/src/bundle/write-elements.ts b/packages/utils/blueprint-cli/src/bundle/write-elements.ts
index 855511b23..397de1eb7 100644
--- a/packages/utils/blueprint-cli/src/bundle/write-elements.ts
+++ b/packages/utils/blueprint-cli/src/bundle/write-elements.ts
@@ -27,9 +27,9 @@ export async function writeElements(
     const sourceLocation = path.join(folderPathAbs, ExportableResource.SRC);
     fs.mkdirSync(sourceLocation);
     for (const repositoryName of repositories) {
-      const cloneCommand = ['git', 'clone', options.bundle.code[repositoryName].clone].join(' ');
-      logger.debug(`Running: ${cloneCommand}`);
-      cp.execSync(cloneCommand, {
+      const cloneArgs = ['clone', options.bundle.code[repositoryName].clone];
+      logger.debug(`Running: git ${cloneArgs.join(' ')}`);
+      cp.execFileSync('git', cloneArgs, {
         stdio: 'inherit',
         cwd: sourceLocation,
       });
diff --git a/packages/utils/blueprint-cli/src/resynth-drivers/resynth.ts b/packages/utils/blueprint-cli/src/resynth-drivers/resynth.ts
index ba16a3ccd..025bcfaae 100644
--- a/packages/utils/blueprint-cli/src/resynth-drivers/resynth.ts
+++ b/packages/utils/blueprint-cli/src/resynth-drivers/resynth.ts
@@ -107,11 +107,7 @@ export async function resynthesize(log: pino.BaseLogger, options: ResynthesizeOp
   try {
     // if something already exists at the output location, we remove it.
     log.debug('cleaning up existing code at resynth resolved output location: %s', resolvedLocation);
-    const cleanCommand = `rm -rf ${resolvedLocation}`;
-    cp.execSync(cleanCommand, {
-      stdio: 'inherit',
-      cwd: options.blueprint,
-    });
+    fs.rmSync(path.resolve(options.blueprint, resolvedLocation), { recursive: true, force: true });
 
     const timeStart = Date.now();
     executeResynthesisCommand(log, options.blueprint, options.jobname, {
@@ -220,24 +216,21 @@ const executeResynthesisCommand = (
     envVariables?: { [key: string]: string };
   },
 ) => {
-  cp.execSync(`mkdir -p ${options.outputDirectory}`, {
-    stdio: 'inherit',
-    cwd,
-  });
+  fs.mkdirSync(options.outputDirectory, { recursive: true });
 
-  const command = [
-    `npx ${options.driver.runtime}`,
-    `${options.driver.path}`,
-    `'${JSON.stringify(options.options)}'`,
-    `${options.outputDirectory}`,
-    `${options.entropy}`,
-    `${options.ancestorBundleDirectory}`,
-    `${options.existingBundleDirectory}`,
-    `${options.proposedBundleDirectory}`,
-  ].join(' ');
+  const resynthArgs = [
+    options.driver.runtime,
+    options.driver.path,
+    JSON.stringify(options.options),
+    options.outputDirectory,
+    options.entropy,
+    options.ancestorBundleDirectory,
+    options.existingBundleDirectory,
+    options.proposedBundleDirectory,
+  ];
 
-  logger.debug(`[${jobname}] reynthesis Command: ${command}`);
-  cp.execSync(command, {
+  logger.debug(`[${jobname}] reynthesis Command: npx ${resynthArgs.join(' ')}`);
+  cp.execFileSync('npx', resynthArgs, {
     stdio: 'inherit',
     cwd,
     env: {
diff --git a/packages/utils/blueprint-cli/src/synth-drivers/cache.ts b/packages/utils/blueprint-cli/src/synth-drivers/cache.ts
index 04ddce59e..57cf39e4c 100644
--- a/packages/utils/blueprint-cli/src/synth-drivers/cache.ts
+++ b/packages/utils/blueprint-cli/src/synth-drivers/cache.ts
@@ -53,7 +53,7 @@ const fsLinkerPlugin = {
   name: 'fs_linker',
   setup(build: any) {
     build.onStart(() => {
-      cp.execSync('rm -rf ./lib/externals');
+      fs.rmSync('./lib/externals', { recursive: true, force: true });
     });
 
     build.onLoad({ filter: /\.(t|j)s/ }, ({ path: filePath }) => {
@@ -73,9 +73,16 @@ const fsLinkerPlugin = {
           const filesSegments = filePath.split('/');
           const rootPkg = findParentPackageDir(filesSegments.slice(0, filesSegments.length - 1).join('/'));
           const pkgName = JSON.parse(fs.readFileSync(`${rootPkg}/package.json`, { encoding: 'utf-8' })).name;
-          cp.execSync(
-            `mkdir -p ./lib/externals/${pkgName} && rsync -a ${rootPkg} ./lib/externals/${pkgName} --include="*/" --exclude="node_modules/**" --prune-empty-dirs`,
-          );
+          const externalsDir = `./lib/externals/${pkgName}`;
+          fs.mkdirSync(externalsDir, { recursive: true });
+          cp.execFileSync('rsync', [
+            '-a',
+            rootPkg,
+            externalsDir,
+            '--include=*/',
+            '--exclude=node_modules/**',
+            '--prune-empty-dirs',
+          ]);
         }
         return {
           contents,
@@ -116,11 +123,9 @@ export const createCache = async (
     resynthCacheFile,
   ];
   cleanup.forEach(file => {
-    if (fs.existsSync(path.join(params.buildDirectory, file))) {
-      cp.execSync(`rm -rf ${file}`, {
-        stdio: 'inherit',
-        cwd: params.buildDirectory,
-      });
+    const filePath = path.join(params.buildDirectory, file);
+    if (fs.existsSync(filePath)) {
+      fs.rmSync(filePath, { recursive: true, force: true });
     }
   });
 
@@ -147,16 +152,10 @@ export const createCache = async (
   }));
 
   // clean up the synth driver
-  cp.execSync(`rm ${synthDriver}`, {
-    stdio: 'inherit',
-    cwd: params.buildDirectory,
-  });
+  fs.rmSync(path.join(params.buildDirectory, synthDriver), { force: true });
 
   // clean up the resynth driver
-  cp.execSync(`rm ${resynthDriver}`, {
-    stdio: 'inherit',
-    cwd: params.buildDirectory,
-  });
+  fs.rmSync(path.join(params.buildDirectory, resynthDriver), { force: true });
 
   return {
     synthDriver: path.join(params.buildDirectory, synthCacheFile),
diff --git a/packages/utils/blueprint-cli/src/synth-drivers/synth-driver.ts b/packages/utils/blueprint-cli/src/synth-drivers/synth-driver.ts
index 52fb5cf2f..71194eae1 100644
--- a/packages/utils/blueprint-cli/src/synth-drivers/synth-driver.ts
+++ b/packages/utils/blueprint-cli/src/synth-drivers/synth-driver.ts
@@ -1,4 +1,3 @@
-import * as cp from 'child_process';
 import * as fs from 'fs';
 import * as path from 'path';
 import * as deepmerge from 'deepmerge';
@@ -132,9 +131,7 @@ export const makeDriverFile = async (
 
 export const cleanUpDriver = (log: pino.BaseLogger, file: DriverFile) => {
   log.debug(`Cleaning up driver: ${file.path}`);
-  cp.execSync(`rm ${file.path}`, {
-    stdio: 'inherit',
-  });
+  fs.rmSync(file.path, { force: true });
 };
 
 /**
diff --git a/packages/utils/blueprint-cli/src/synth-drivers/synth.ts b/packages/utils/blueprint-cli/src/synth-drivers/synth.ts
index 2f3ef0923..05c932c79 100644
--- a/packages/utils/blueprint-cli/src/synth-drivers/synth.ts
+++ b/packages/utils/blueprint-cli/src/synth-drivers/synth.ts
@@ -67,11 +67,7 @@ export async function synthesize(log: pino.BaseLogger, options: SynthOptions) {
   try {
     // if something already exists at the synthesis location, we remove it.
     log.debug('cleaning up existing code at synth location: %s', options.outputDirectory);
-    const cleanCommand = `rm -rf ${options.outputDirectory}`;
-    cp.execSync(cleanCommand, {
-      stdio: 'inherit',
-      cwd: options.blueprintPath,
-    });
+    fs.rmSync(path.resolve(options.blueprintPath, options.outputDirectory), { recursive: true, force: true });
 
     const timeStart = Date.now();
     executeSynthesisCommand(log, options.blueprintPath, options.jobname, {
@@ -127,20 +123,18 @@ function executeSynthesisCommand(
     envVariables: { [key: string]: string };
   },
 ) {
-  cp.execSync(`mkdir -p ${options.outputDirectory}`, {
-    stdio: 'inherit',
-    cwd,
-  });
-  const synthCommand = [
-    `npx ${options.driver.runtime}`,
-    `${options.driver.path}`,
-    `'${JSON.stringify(options.options)}'`,
-    `'${options.outputDirectory}'`,
-    `'${options.entropy}'`,
-  ].join(' ');
-
-  logger.debug(`[${jobname}] Synthesis Command: ${synthCommand}`);
-  cp.execSync(synthCommand, {
+  fs.mkdirSync(options.outputDirectory, { recursive: true });
+
+  const synthArgs = [
+    options.driver.runtime,
+    options.driver.path,
+    JSON.stringify(options.options),
+    options.outputDirectory,
+    options.entropy,
+  ];
+
+  logger.debug(`[${jobname}] Synthesis Command: npx ${synthArgs.join(' ')}`);
+  cp.execFileSync('npx', synthArgs, {
     stdio: 'inherit',
     cwd,
     env: {