diff --git a/luni/src/test/java/libcore/javax/security/auth/x500/X500PrincipalTest.java b/luni/src/test/java/libcore/javax/security/auth/x500/X500PrincipalTest.java
index 4f5d658..5471b1f 100644
--- a/luni/src/test/java/libcore/javax/security/auth/x500/X500PrincipalTest.java
+++ b/luni/src/test/java/libcore/javax/security/auth/x500/X500PrincipalTest.java
@@ -120,6 +120,30 @@
         expectExceptionInDNConstructor("l=\\g0");
     }
 
+    public void testNegativeLen() {
+        try {
+            X500Principal p = new X500Principal(new byte[]{
+                    0x30, // DerValue.tag_Sequence read in DerValue#getSequence
+                    9,    // Length of the vector. read in readVector.
+                          // DerInputStream.getLength will just return this as 10 & 0x80 == 0
+                    -1,   // Tag of the first value in the sequencevalue. Convenient so that it
+                          // doesn't hold DerIndefLenConverter.isEOC()
+                    (byte) 0x80, // Encoding in indefinite form
+                    -1,          // Second tag to be read by DerIndefLenConverter
+                    (byte) 0x84, // Second length byte to be read, 0x80 means long form, 4 bytes
+                    (byte) 0xff, // Length to be read by DerIndefLenConverter, -6, will move the
+                                 // buffer position to the second tag
+                    (byte) 0xff,
+                    (byte) 0xff,
+                    (byte) -6,
+                    0,           // Needed as otherwise it's detected that there's nothing after
+                    // the length
+            });
+            fail("expected IllegalArgumentException");
+        } catch (IllegalArgumentException expected) {
+        }
+    }
+
     private void expectExceptionInDNConstructor(String dn) {
         try {
             X500Principal principal = new X500Principal(dn);
diff --git a/ojluni/src/main/java/sun/security/util/DerIndefLenConverter.java b/ojluni/src/main/java/sun/security/util/DerIndefLenConverter.java
index 78d9e30..cbd5ecc 100755
--- a/ojluni/src/main/java/sun/security/util/DerIndefLenConverter.java
+++ b/ojluni/src/main/java/sun/security/util/DerIndefLenConverter.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2008, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -156,12 +156,18 @@
         }
         if (isLongForm(lenByte)) {
             lenByte &= LEN_MASK;
-            if (lenByte > 4)
+            if (lenByte > 4) {
                 throw new IOException("Too much data");
-            if ((dataSize - dataPos) < (lenByte + 1))
+            }
+            if ((dataSize - dataPos) < (lenByte + 1)) {
                 throw new IOException("Too little data");
-            for (int i = 0; i < lenByte; i++)
+            }
+            for (int i = 0; i < lenByte; i++) {
                 curLen = (curLen << 8) + (data[dataPos++] & 0xff);
+            }
+            if (curLen < 0) {
+                throw new IOException("Invalid length bytes");
+            }
         } else {
            curLen = (lenByte & LEN_MASK);
         }
@@ -188,10 +194,15 @@
         }
         if (isLongForm(lenByte)) {
             lenByte &= LEN_MASK;
-            for (int i = 0; i < lenByte; i++)
+            for (int i = 0; i < lenByte; i++) {
                 curLen = (curLen << 8) + (data[dataPos++] & 0xff);
-        } else
+            }
+            if (curLen < 0) {
+                throw new IOException("Invalid length bytes");
+            }
+        } else {
             curLen = (lenByte & LEN_MASK);
+        }
         writeLength(curLen);
         writeValue(curLen);
     }
diff --git a/ojluni/src/main/java/sun/security/util/DerInputStream.java b/ojluni/src/main/java/sun/security/util/DerInputStream.java
index 8f51439..dae8afd 100755
--- a/ojluni/src/main/java/sun/security/util/DerInputStream.java
+++ b/ojluni/src/main/java/sun/security/util/DerInputStream.java
@@ -604,6 +604,10 @@
                 value <<= 8;
                 value += 0x0ff & in.read();
             }
+            if (value < 0) {
+                throw new IOException("DerInputStream.getLength(): "
+                        + "Invalid length bytes");
+            }
         }
         return value;
     }