diff --git a/lib/internal/crypto/cfrg.js b/lib/internal/crypto/cfrg.js
index c5bbaae90cf595..fd3f168435ddcb 100644
--- a/lib/internal/crypto/cfrg.js
+++ b/lib/internal/crypto/cfrg.js
@@ -2,6 +2,7 @@
 
 const {
   SafeSet,
+  StringPrototypeToLowerCase,
 } = primordials;
 
 const { Buffer } = require('buffer');
@@ -332,7 +333,7 @@ function cfrgImportKey(
       return undefined;
   }
 
-  if (keyObject.asymmetricKeyType !== name.toLowerCase()) {
+  if (keyObject.asymmetricKeyType !== StringPrototypeToLowerCase(name)) {
     throw lazyDOMException('Invalid key type', 'DataError');
   }
 
diff --git a/lib/internal/crypto/ml_dsa.js b/lib/internal/crypto/ml_dsa.js
index ebe3bfe3d17ca0..f4df51ae7cb6aa 100644
--- a/lib/internal/crypto/ml_dsa.js
+++ b/lib/internal/crypto/ml_dsa.js
@@ -2,6 +2,7 @@
 
 const {
   SafeSet,
+  StringPrototypeToLowerCase,
   TypedArrayPrototypeGetBuffer,
   TypedArrayPrototypeSet,
   Uint8Array,
@@ -276,7 +277,7 @@ function mlDsaImportKey(
       return undefined;
   }
 
-  if (keyObject.asymmetricKeyType !== name.toLowerCase()) {
+  if (keyObject.asymmetricKeyType !== StringPrototypeToLowerCase(name)) {
     throw lazyDOMException('Invalid key type', 'DataError');
   }
 
diff --git a/lib/internal/crypto/ml_kem.js b/lib/internal/crypto/ml_kem.js
index f6eb76cef10b20..208913cae86c36 100644
--- a/lib/internal/crypto/ml_kem.js
+++ b/lib/internal/crypto/ml_kem.js
@@ -3,6 +3,7 @@
 const {
   PromiseWithResolvers,
   SafeSet,
+  StringPrototypeToLowerCase,
   TypedArrayPrototypeGetBuffer,
   TypedArrayPrototypeSet,
   Uint8Array,
@@ -209,7 +210,7 @@ function mlKemImportKey(
       return undefined;
   }
 
-  if (keyObject.asymmetricKeyType !== name.toLowerCase()) {
+  if (keyObject.asymmetricKeyType !== StringPrototypeToLowerCase(name)) {
     throw lazyDOMException('Invalid key type', 'DataError');
   }
 
diff --git a/lib/internal/crypto/util.js b/lib/internal/crypto/util.js
index 96abe6a04b28e1..ab10c53a655a60 100644
--- a/lib/internal/crypto/util.js
+++ b/lib/internal/crypto/util.js
@@ -15,7 +15,7 @@ const {
   ObjectEntries,
   ObjectKeys,
   ObjectPrototypeHasOwnProperty,
-  Promise,
+  PromiseWithResolvers,
   StringPrototypeToUpperCase,
   Symbol,
   TypedArrayPrototypeGetBuffer,
@@ -656,15 +656,15 @@ function onDone(resolve, reject, err, result) {
 }
 
 function jobPromise(getJob) {
-  return new Promise((resolve, reject) => {
-    try {
-      const job = getJob();
-      job.ondone = FunctionPrototypeBind(onDone, job, resolve, reject);
-      job.run();
-    } catch (err) {
-      onDone(resolve, reject, err);
-    }
-  });
+  const { promise, resolve, reject } = PromiseWithResolvers();
+  try {
+    const job = getJob();
+    job.ondone = FunctionPrototypeBind(onDone, job, resolve, reject);
+    job.run();
+  } catch (err) {
+    onDone(resolve, reject, err);
+  }
+  return promise;
 }
 
 // In WebCrypto, the publicExponent option in RSA is represented as a
diff --git a/lib/internal/crypto/webidl.js b/lib/internal/crypto/webidl.js
index e72931e9c83cca..4162d84d426f53 100644
--- a/lib/internal/crypto/webidl.js
+++ b/lib/internal/crypto/webidl.js
@@ -195,12 +195,14 @@ converters.object = (V, opts) => {
 
 const isNonSharedArrayBuffer = isArrayBuffer;
 
+/**
+ * @param {string | object} V - The hash algorithm identifier (string or object).
+ * @param {string} label - The dictionary name for the error message.
+ */
 function ensureSHA(V, label) {
-  if (
-    typeof V === 'string' ?
-      !StringPrototypeStartsWith(StringPrototypeToLowerCase(V), 'sha') :
-      V.name?.toLowerCase?.().startsWith('sha') === false
-  )
+  const name = typeof V === 'string' ? V : V.name;
+  if (typeof name !== 'string' ||
+      !StringPrototypeStartsWith(StringPrototypeToLowerCase(name), 'sha'))
     throw lazyDOMException(
       `Only SHA hashes are supported in ${label}`, 'NotSupportedError');
 }
diff --git a/test/parallel/test-webcrypto-promise-prototype-pollution.mjs b/test/parallel/test-webcrypto-promise-prototype-pollution.mjs
new file mode 100644
index 00000000000000..b4fbedba5e3242
--- /dev/null
+++ b/test/parallel/test-webcrypto-promise-prototype-pollution.mjs
@@ -0,0 +1,95 @@
+import * as common from '../common/index.mjs';
+
+if (!common.hasCrypto) common.skip('missing crypto');
+
+// WebCrypto subtle methods must not leak intermediate values
+// through Promise.prototype.then pollution.
+// Regression test for https://github.com/nodejs/node/pull/61492
+// and https://github.com/nodejs/node/issues/59699.
+
+import { hasOpenSSL } from '../common/crypto.js';
+
+const { subtle } = globalThis.crypto;
+
+Promise.prototype.then = common.mustNotCall('Promise.prototype.then');
+
+await subtle.digest('SHA-256', new Uint8Array([1, 2, 3]));
+
+await subtle.generateKey({ name: 'AES-CBC', length: 256 }, true, ['encrypt', 'decrypt']);
+
+await subtle.generateKey({ name: 'ECDSA', namedCurve: 'P-256' }, true, ['sign', 'verify']);
+
+const rawKey = globalThis.crypto.getRandomValues(new Uint8Array(32));
+
+const importedKey = await subtle.importKey(
+  'raw', rawKey, { name: 'AES-CBC', length: 256 }, false, ['encrypt', 'decrypt']);
+
+const exportableKey = await subtle.importKey(
+  'raw', rawKey, { name: 'AES-CBC', length: 256 }, true, ['encrypt', 'decrypt']);
+
+await subtle.exportKey('raw', exportableKey);
+
+const iv = globalThis.crypto.getRandomValues(new Uint8Array(16));
+const plaintext = new TextEncoder().encode('Hello, world!');
+
+const ciphertext = await subtle.encrypt({ name: 'AES-CBC', iv }, importedKey, plaintext);
+
+await subtle.decrypt({ name: 'AES-CBC', iv }, importedKey, ciphertext);
+
+const signingKey = await subtle.generateKey(
+  { name: 'HMAC', hash: 'SHA-256' }, false, ['sign', 'verify']);
+
+const data = new TextEncoder().encode('test data');
+
+const signature = await subtle.sign('HMAC', signingKey, data);
+
+await subtle.verify('HMAC', signingKey, signature, data);
+
+const pbkdf2Key = await subtle.importKey(
+  'raw', rawKey, 'PBKDF2', false, ['deriveBits', 'deriveKey']);
+
+await subtle.deriveBits(
+  { name: 'PBKDF2', salt: rawKey, iterations: 1000, hash: 'SHA-256' },
+  pbkdf2Key, 256);
+
+await subtle.deriveKey(
+  { name: 'PBKDF2', salt: rawKey, iterations: 1000, hash: 'SHA-256' },
+  pbkdf2Key,
+  { name: 'AES-CBC', length: 256 },
+  true,
+  ['encrypt', 'decrypt']);
+
+const wrappingKey = await subtle.generateKey(
+  { name: 'AES-KW', length: 256 }, true, ['wrapKey', 'unwrapKey']);
+
+const keyToWrap = await subtle.generateKey(
+  { name: 'AES-CBC', length: 256 }, true, ['encrypt', 'decrypt']);
+
+const wrapped = await subtle.wrapKey('raw', keyToWrap, wrappingKey, 'AES-KW');
+
+await subtle.unwrapKey(
+  'raw', wrapped, wrappingKey, 'AES-KW',
+  { name: 'AES-CBC', length: 256 }, true, ['encrypt', 'decrypt']);
+
+const { privateKey } = await subtle.generateKey(
+  { name: 'ECDSA', namedCurve: 'P-256' }, true, ['sign', 'verify']);
+
+await subtle.getPublicKey(privateKey, ['verify']);
+
+if (hasOpenSSL(3, 5)) {
+  const kemPair = await subtle.generateKey(
+    { name: 'ML-KEM-768' }, false,
+    ['encapsulateKey', 'encapsulateBits', 'decapsulateKey', 'decapsulateBits']);
+
+  const { ciphertext: ct1 } = await subtle.encapsulateKey(
+    { name: 'ML-KEM-768' }, kemPair.publicKey, 'HKDF', false, ['deriveBits']);
+
+  await subtle.decapsulateKey(
+    { name: 'ML-KEM-768' }, kemPair.privateKey, ct1, 'HKDF', false, ['deriveBits']);
+
+  const { ciphertext: ct2 } = await subtle.encapsulateBits(
+    { name: 'ML-KEM-768' }, kemPair.publicKey);
+
+  await subtle.decapsulateBits(
+    { name: 'ML-KEM-768' }, kemPair.privateKey, ct2);
+}