diff --git a/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoAlgorithmNames.qll b/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoAlgorithmNames.qll
index 8275fdd83e60..c828a804fb85 100644
--- a/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoAlgorithmNames.qll
+++ b/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoAlgorithmNames.qll
@@ -22,6 +22,14 @@ predicate isSymmetricAlgorithm(string name) {
     ]
 }
 
+predicate isHmacAlgorithm(string name) {
+  name =
+    [
+      "hmacmd5", "hmacsha1", "hmacripemd160", "hmacsha256", "hmacsha384", "hmacsha512",
+      "hmacsha3256", "hmacsha3384", "hmacsha3512"
+    ]
+}
+
 predicate isCipherBlockModeAlgorithm(string name) {
   name = ["cbc", "gcm", "ccm", "cfb", "ofb", "cfb8", "ctr", "openpgp", "xts", "eax", "siv", "ecb"]
 }
diff --git a/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoArtifact.qll b/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoArtifact.qll
index 0aa91bff8c43..eb9cd159d61c 100644
--- a/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoArtifact.qll
+++ b/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptoArtifact.qll
@@ -29,6 +29,14 @@ abstract class SymmetricAlgorithm extends CryptographicAlgorithm {
   }
 }
 
+abstract class HmacAlgorithm extends CryptographicAlgorithm {
+  final string getHmacName() {
+    if exists(string n | n = this.getName() and isHmacAlgorithm(n))
+    then result = this.getName()
+    else result = unknownAlgorithm()
+  }
+}
+
 abstract class BlockMode extends CryptographicAlgorithm {
   final string getBlockModeName() {
     if exists(string n | n = this.getName() and isCipherBlockModeAlgorithm(n))
diff --git a/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptographyModule.qll b/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptographyModule.qll
index 0e6b2a434733..e0665792e57a 100644
--- a/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptographyModule.qll
+++ b/powershell/ql/lib/semmle/code/powershell/security/cryptography/CryptographyModule.qll
@@ -176,6 +176,46 @@ class CipherBlockStringConstExpr extends BlockMode {
   override string getName() { result = modeName }
 }
 
+class HmacAlgorithmObjectCreation extends HmacAlgorithm, CryptoAlgorithmObjectCreation {
+  string algName;
+
+  HmacAlgorithmObjectCreation() {
+    objectName = ["", "system.security.cryptography."] + algName and
+    isHmacAlgorithm(algName)
+  }
+
+  override string getName() { result = algName }
+}
+
+class HmacAlgorithmCreateCall extends HmacAlgorithm, DataFlow::CallNode {
+  string algName;
+
+  HmacAlgorithmCreateCall() {
+    isHmacAlgorithm(algName) and
+    this =
+      API::getTopLevelMember("system")
+          .getMember("security")
+          .getMember("cryptography")
+          .getMember(algName)
+          .getMember(["create", "new"])
+          .asCall()
+    
+  }
+
+  override string getName() { result = algName }
+}
+
+class HmacAlgorithmCreateFromNameCall extends HmacAlgorithm, CryptoAlgorithmCreateFromNameCall {
+  string algName;
+
+  HmacAlgorithmCreateFromNameCall() {
+    objectName = ["", "system.security.cryptography."] + algName and
+    isHmacAlgorithm(algName)
+  }
+
+  override string getName() { result = algName }
+}
+
 class CipherBlockModeEnum extends BlockMode {
   string modeName;
 
diff --git a/powershell/ql/src/queries/security/cwe-327/WeakHmac.qhelp b/powershell/ql/src/queries/security/cwe-327/WeakHmac.qhelp
new file mode 100644
index 000000000000..3cfae573f25b
--- /dev/null
+++ b/powershell/ql/src/queries/security/cwe-327/WeakHmac.qhelp
@@ -0,0 +1,24 @@
+<!DOCTYPE qhelp PUBLIC "-//Semmle//qhelp//EN" "qhelp.dtd">
+<qhelp>
+  <overview>
+    <p>
+      HMAC (Hash-based Message Authentication Code) algorithms are used to verify both the
+      integrity and authenticity of messages. Using weak HMAC algorithms such as HMACMD5,
+      HMACSHA1, or HMACRIPEMD160 can compromise message authentication, as the underlying
+      hash functions have known cryptographic weaknesses.
+    </p>
+  </overview>
+  <recommendation>
+    <p>
+      Use a strong HMAC algorithm such as HMACSHA256, HMACSHA384, or HMACSHA512. These are
+      based on the SHA-2 family of hash functions and provide adequate security for message
+      authentication.
+    </p>
+  </recommendation>
+
+  <references>
+    <li>NIST, SP 800-131A: <a href="https://csrc.nist.gov/publications/detail/sp/800-131a/rev-2/final">Transitioning the Use of Cryptographic Algorithms and Key Lengths</a>.</li>
+    <li>CWE-327: <a href="https://cwe.mitre.org/data/definitions/327.html">Use of a Broken or Risky Cryptographic Algorithm</a>.</li>
+    <li>CWE-328: <a href="https://cwe.mitre.org/data/definitions/328.html">Use of Weak Hash</a>.</li>
+  </references>
+</qhelp>
diff --git a/powershell/ql/src/queries/security/cwe-327/WeakHmac.ql b/powershell/ql/src/queries/security/cwe-327/WeakHmac.ql
new file mode 100644
index 000000000000..ca97d69da7d9
--- /dev/null
+++ b/powershell/ql/src/queries/security/cwe-327/WeakHmac.ql
@@ -0,0 +1,21 @@
+/**
+ * @name Use of weak HMAC algorithm
+ * @description Using weak HMAC algorithms like HMACMD5 or HMACSHA1 can compromise message authentication.
+ * @kind problem
+ * @problem.severity warning
+ * @security-severity 7.5
+ * @precision high
+ * @id powershell/weak-hmac
+ * @tags security
+ *       external/cwe/cwe-327
+ *       external/cwe/cwe-328
+ */
+
+import powershell
+import semmle.code.powershell.ApiGraphs
+import semmle.code.powershell.dataflow.DataFlow
+import semmle.code.powershell.security.cryptography.Concepts
+
+from HmacAlgorithm hmacAlg
+where not hmacAlg.getHmacName() = ["hmacsha256", "hmacsha384", "hmacsha512"]
+select hmacAlg, "Use of weak HMAC algorithm: " + hmacAlg.getHmacName() + ". Use HMACSHA256 or stronger."
diff --git a/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/WeakHmac.expected b/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/WeakHmac.expected
new file mode 100644
index 000000000000..a96f5b0fee52
--- /dev/null
+++ b/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/WeakHmac.expected
@@ -0,0 +1,4 @@
+| test.ps1:6:9:6:55 | Call to new-object | Use of weak HMAC algorithm: hmacmd5. Use HMACSHA256 or stronger. |
+| test.ps1:9:9:9:56 | Call to new-object | Use of weak HMAC algorithm: hmacsha1. Use HMACSHA256 or stronger. |
+| test.ps1:12:9:12:56 | Call to create | Use of weak HMAC algorithm: hmacmd5. Use HMACSHA256 or stronger. |
+| test.ps1:15:9:15:54 | Call to new | Use of weak HMAC algorithm: hmacsha1. Use HMACSHA256 or stronger. |
diff --git a/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/WeakHmac.qlref b/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/WeakHmac.qlref
new file mode 100644
index 000000000000..f6476ddc9c32
--- /dev/null
+++ b/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/WeakHmac.qlref
@@ -0,0 +1 @@
+queries/security/cwe-327/WeakHmac.ql
diff --git a/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/test.ps1 b/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/test.ps1
new file mode 100644
index 000000000000..a07d3b9b05ba
--- /dev/null
+++ b/powershell/ql/test/query-tests/security/cwe-327/WeakHmac/test.ps1
@@ -0,0 +1,28 @@
+# ===================================================================
+# ========== TRUE POSITIVES (should trigger alert) ==================
+# ===================================================================
+
+# --- Case 1: HMACMD5 via New-Object ---
+$hmac = New-Object System.Security.Cryptography.HMACMD5 # BAD
+
+# --- Case 2: HMACSHA1 via New-Object ---
+$hmac = New-Object System.Security.Cryptography.HMACSHA1 # BAD
+
+# --- Case 3: HMACMD5 via static Create ---
+$hmac = [System.Security.Cryptography.HMACMD5]::Create() # BAD
+
+# --- Case 4: HMACSHA1 via ::new() ---
+$hmac = [System.Security.Cryptography.HMACSHA1]::new() # BAD
+
+# ===================================================================
+# ========== TRUE NEGATIVES (should NOT trigger alert) ==============
+# ===================================================================
+
+# --- Safe: HMACSHA256 ---
+$hmac = New-Object System.Security.Cryptography.HMACSHA256 # GOOD
+
+# --- Safe: HMACSHA384 ---
+$hmac = [System.Security.Cryptography.HMACSHA384]::new() # GOOD
+
+# --- Safe: HMACSHA512 ---
+$hmac = [System.Security.Cryptography.HMACSHA512]::Create() # GOOD