diff --git a/lib/utils/allow-scripts-writer.js b/lib/utils/allow-scripts-writer.js
index 6964279f2f2e0..a777b2c3964bd 100644
--- a/lib/utils/allow-scripts-writer.js
+++ b/lib/utils/allow-scripts-writer.js
@@ -3,6 +3,7 @@ const { log } = require('proc-log')
 const {
   getTrustedRegistryIdentity,
   resolvedSourceSpecs,
+  normalizeFileSpec,
 } = require('@npmcli/arborist/lib/script-allowed.js')
 
 // Pure helpers that implement the RFC's pin-mismatch table for
@@ -56,8 +57,8 @@ const versionedKeyFor = (node) => {
     )
     return null
   }
-  /* istanbul ignore next: 'file:' and '/' branches are each covered separately */
-  if (resolved.startsWith('file:') || resolved.startsWith('/')) {
+  /* istanbul ignore next: 'file:', '/', and Windows drive letter branches are covered */
+  if (resolved.startsWith('file:') || resolved.startsWith('/') || /^[a-zA-Z]:[\\/]/.test(resolved)) {
     return resolved
   }
   // No trusted source. Refuse to compose a key from attacker-controlled
@@ -86,7 +87,7 @@ const nameKeyFor = (node) => {
     }
     return null
   }
-  if (resolved.startsWith('file:') || resolved.startsWith('/')) {
+  if (resolved.startsWith('file:') || resolved.startsWith('/') || /^[a-zA-Z]:[\\/]/.test(resolved)) {
     return resolved
   }
   // Registry deps: only the URL-derived (or edges-derived, in the
@@ -179,6 +180,16 @@ const keyTargetsNode = (key, node) => {
     }
     case 'file':
     case 'directory':
+      return resolvedSourceSpecs(node)
+        .some(resolved => {
+          const normResolved = normalizeFileSpec(resolved)
+          const normSave = normalizeFileSpec(parsed.saveSpec)
+          const normFetch = normalizeFileSpec(parsed.fetchSpec)
+          return (
+            (normSave !== '' && normResolved === normSave) ||
+            (normFetch !== '' && normResolved === normFetch)
+          )
+        })
     case 'remote':
       return resolvedSourceSpecs(node)
         .some(resolved => resolved === parsed.saveSpec || resolved === parsed.fetchSpec)
diff --git a/workspaces/arborist/lib/script-allowed.js b/workspaces/arborist/lib/script-allowed.js
index 8c9b3fe118a8e..152f6ed05cc50 100644
--- a/workspaces/arborist/lib/script-allowed.js
+++ b/workspaces/arborist/lib/script-allowed.js
@@ -327,9 +327,25 @@ const matchGit = (node, parsed) => {
   return nodeCommittish.startsWith(keyCommittish)
 }
 
+const normalizeFileSpec = (spec) => {
+  if (typeof spec !== 'string' || spec === '') {
+    return ''
+  }
+  const withoutFile = spec.startsWith('file:') ? spec.slice(5) : spec
+  return withoutFile.replace(/\\/g, '/')
+}
+
 const matchFileOrDir = (node, parsed) => {
+  const normSave = normalizeFileSpec(parsed.saveSpec)
+  const normFetch = normalizeFileSpec(parsed.fetchSpec)
   return resolvedSourceSpecs(node)
-    .some(resolved => resolved === parsed.saveSpec || resolved === parsed.fetchSpec)
+    .some(resolved => {
+      const normResolved = normalizeFileSpec(resolved)
+      return (
+        (normSave !== '' && normResolved === normSave) ||
+        (normFetch !== '' && normResolved === normFetch)
+      )
+    })
 }
 
 const matchRemote = (node, parsed) => {
@@ -382,3 +398,4 @@ module.exports.isExactVersionDisjunction = isExactVersionDisjunction
 module.exports.getTrustedRegistryIdentity = getTrustedRegistryIdentity
 module.exports.resolvedSourceSpecs = resolvedSourceSpecs
 module.exports.trustedDisplay = trustedDisplay
+module.exports.normalizeFileSpec = normalizeFileSpec
diff --git a/workspaces/arborist/test/script-allowed.js b/workspaces/arborist/test/script-allowed.js
index 218ccf1e28888..78abcda9c545b 100644
--- a/workspaces/arborist/test/script-allowed.js
+++ b/workspaces/arborist/test/script-allowed.js
@@ -196,6 +196,42 @@ t.test('local tarball key — npa parses *.tgz paths as type=file', t => {
   t.end()
 })
 
+t.test('local tarball key — Windows backslashes and file: prefix matching', t => {
+  const winTgzNode = node({
+    name: 'electron-winstaller',
+    packageName: 'electron-winstaller',
+    version: '5.3.0',
+    resolved: 'file:C:\\absolute\\path\\to\\electron-winstaller-5.3.0.tgz',
+  })
+
+  // Matches forward slash file: URI
+  t.equal(isScriptAllowed(winTgzNode, {
+    'file:C:/absolute/path/to/electron-winstaller-5.3.0.tgz': true,
+  }), true)
+
+  // Matches backslash file: URI
+  t.equal(isScriptAllowed(winTgzNode, {
+    'file:C:\\absolute\\path\\to\\electron-winstaller-5.3.0.tgz': true,
+  }), true)
+
+  // Matches absolute path without file: prefix
+  t.equal(isScriptAllowed(winTgzNode, {
+    'C:/absolute/path/to/electron-winstaller-5.3.0.tgz': true,
+  }), true)
+
+  // Deny wins
+  t.equal(isScriptAllowed(winTgzNode, {
+    'file:C:/absolute/path/to/electron-winstaller-5.3.0.tgz': false,
+  }), false)
+
+  // Unrelated path does not match
+  t.equal(isScriptAllowed(winTgzNode, {
+    'file:C:/other/path/to/pkg.tgz': true,
+  }), null)
+
+  t.end()
+})
+
 t.test('remote tarball — exact resolved match', t => {
   const remoteNode = node({
     name: 'pkg',