diff --git a/phpseclib/File/ASN1.php b/phpseclib/File/ASN1.php
index 099e1ec0..dba99de7 100644
--- a/phpseclib/File/ASN1.php
+++ b/phpseclib/File/ASN1.php
@@ -1176,6 +1176,11 @@ class ASN1
         $oid = array();
         $pos = 0;
         $len = strlen($content);
+        // see https://github.com/openjdk/jdk/blob/2deb318c9f047ec5a4b160d66a4b52f93688ec42/src/java.base/share/classes/sun/security/util/ObjectIdentifier.java#L55
+        if ($len > 4096) {
+            //user_error('Object Identifier size is limited to 4096 bytes');
+            return false;
+        }
 
         if (ord($content[$len - 1]) & 0x80) {
             return false;
diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index 81b69ace..fd9cd578 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -729,6 +729,33 @@ class BigInteger
         return $result;
     }
 
+    /**
+     * Return the size of a BigInteger in bits
+     *
+     * @return int
+     */
+    function getLength()
+    {
+        if (MATH_BIGINTEGER_MODE != MATH_BIGINTEGER_MODE_INTERNAL) {
+            return strlen($this->toBits());
+        }
+
+        $max = count($this->value) - 1;
+        return $max != -1 ?
+            $max * MATH_BIGINTEGER_BASE + ceil(log($a->value[$max] + 1, 2)) :
+            0;
+    }
+
+    /**
+     * Return the size of a BigInteger in bytes
+     *
+     * @return int
+     */
+    function getLengthInBytes()
+    {
+        return ceil($this->getLength() / 8);
+    }
+
     /**
      * Copy an object
      *
@@ -3237,6 +3264,11 @@ class BigInteger
             $min = $temp;
         }
 
+        $length = $max->getLength();
+        if ($length > 8196) {
+            user_error('Generation of random prime numbers larger than 8196 has been disabled');
+        }
+
         static $one, $two;
         if (!isset($one)) {
             $one = new static(1);
@@ -3344,7 +3376,14 @@ class BigInteger
      */
     function isPrime($t = false)
     {
-        $length = strlen($this->toBytes());
+        $length = $this->getLength();
+        // OpenSSL limits RSA keys to 16384 bits. The length of an RSA key is equal to the length of the modulo, which is
+        // produced by multiplying the primes p and q by one another. The largest number two 8196 bit primes can produce is
+        // a 16384 bit number so, basically, 8196 bit primes are the largest OpenSSL will generate and if that's the largest
+        // that it'll generate it also stands to reason that that's the largest you'll be able to test primality on
+        if ($length > 8196) {
+            user_error('Primality testing is not supported for numbers larger than 8196 bits');
+        }
 
         if (!$t) {
             // see HAC 4.49 "Note (controlling the error probability)"
diff --git a/tests/Unit/File/ASN1/mal-cert-02.der b/tests/Unit/File/ASN1/mal-cert-02.der
new file mode 100644
index 00000000..981c3557
Binary files /dev/null and b/tests/Unit/File/ASN1/mal-cert-02.der differ
diff --git a/tests/Unit/File/ASN1Test.php b/tests/Unit/File/ASN1Test.php
index d371154e..486809a2 100644
--- a/tests/Unit/File/ASN1Test.php
+++ b/tests/Unit/File/ASN1Test.php
@@ -448,4 +448,17 @@ class Unit_File_ASN1Test extends PhpseclibTestCase
         $decoded = $asn1->decodeBER($em);
         $this->assertFalse($decoded[0]);
     }
+
+    public function testLongOID()
+    {
+        $cert = file_get_contents(dirname(__FILE__) . '/ASN1/mal-cert-02.der');
+
+        $asn1 = new File_ASN1();
+        //$this->setExpectedException('PHPUnit_Framework_Error_Notice');
+        $decoded = $asn1->decodeBER($cert);
+        $this->assertFalse($decoded[0]);
+
+        //$x509 = new X509();
+        //$x509->loadX509($cert);
+    }
 }