diff --git a/src/CertManager.sol b/src/CertManager.sol
index 29ecfd0..fd18c88 100644
--- a/src/CertManager.sol
+++ b/src/CertManager.sol
@@ -432,6 +432,14 @@ contract CertManager is ICertManager {
         Asn1Ptr subjectPublicKeyPtr = certificate.nextSiblingOf(pubKeyAlgoPtr);
         Asn1Ptr subjectPubKeyPtr = certificate.bitstring(subjectPublicKeyPtr);
 
+        if (
+            algoParamsPtr.header() + algoParamsPtr.totalLength() != pubKeyAlgoPtr.header() + pubKeyAlgoPtr.totalLength()
+                || subjectPublicKeyPtr.header() + subjectPublicKeyPtr.totalLength()
+                    != subjectPublicKeyInfoPtr.header() + subjectPublicKeyInfoPtr.totalLength()
+        ) {
+            revert InvalidSubjectPublicKey();
+        }
+
         if (certificate.keccak(pubKeyAlgoIdPtr.content(), pubKeyAlgoIdPtr.length()) != EC_PUB_KEY_OID) {
             revert InvalidSubjectPublicKey();
         }
diff --git a/test/CertManager.t.sol b/test/CertManager.t.sol
index 6db1293..8bd1beb 100644
--- a/test/CertManager.t.sol
+++ b/test/CertManager.t.sol
@@ -173,6 +173,27 @@ contract CertManagerTest is Test {
         assertEq(certManagerPubKeyHarness.parsePubKey(spki), pubKey);
     }
 
+    function test_ParsePubKeyRejectsTrailingAlgorithmIdentifierFields() public {
+        bytes memory pubKey = _patternBytes(96);
+        bytes memory algorithmIdentifier =
+            _derNode(0x30, bytes.concat(hex"06072a8648ce3d0201", hex"06052b81040022", hex"0500"));
+        bytes memory subjectPublicKey = _derNode(0x03, bytes.concat(hex"0004", pubKey));
+        bytes memory spki = _derNode(0x30, bytes.concat(algorithmIdentifier, subjectPublicKey));
+
+        vm.expectRevert(CertManager.InvalidSubjectPublicKey.selector);
+        certManagerPubKeyHarness.parsePubKey(spki);
+    }
+
+    function test_ParsePubKeyRejectsTrailingSubjectPublicKeyInfoFields() public {
+        bytes memory pubKey = _patternBytes(96);
+        bytes memory algorithmIdentifier = _derNode(0x30, hex"06072a8648ce3d020106052b81040022");
+        bytes memory subjectPublicKey = _derNode(0x03, bytes.concat(hex"0004", pubKey));
+        bytes memory spki = _derNode(0x30, bytes.concat(algorithmIdentifier, subjectPublicKey, hex"0500"));
+
+        vm.expectRevert(CertManager.InvalidSubjectPublicKey.selector);
+        certManagerPubKeyHarness.parsePubKey(spki);
+    }
+
     function test_ParsePubKeyRejectsCompressedP384Point() public {
         bytes memory compressedKey = _patternBytes(48);
         bytes memory spki = abi.encodePacked(hex"3046301006072a8648ce3d020106052b8104002203320002", compressedKey);