diff --git a/ChangeLog b/ChangeLog
index 329e563ec..89caddbc4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -11,6 +11,10 @@ Security
      but might be in other uses. On 32 bit machines, requires reading a string
      of close to or larger than 1GB to exploit; on 64 bit machines, would require
      reading a string of close to or larger than 2^62 bytes.
+   * Fix potential random memory allocation in mbedtls_pem_read_buffer()
+     on crafted PEM input data. Found an fix provided by Guid Vranken.
+     Not triggerable remotely in TLS. Triggerable remotely if you accept PEM
+     data from an untrusted source.
 
 = mbed TLS 1.3.13 reladsed 2015-09-17
 
diff --git a/library/base64.c b/library/base64.c
index ac922a474..2f7bb1428 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -190,7 +190,10 @@ int base64_decode( unsigned char *dst, size_t *dlen,
     }
 
     if( n == 0 )
+    {
+        *dlen = 0;
         return( 0 );
+    }
 
     n = ( ( n * 6 ) + 7 ) >> 3;
     n -= j;
diff --git a/library/pem.c b/library/pem.c
index 5060484cc..054fcffb8 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -317,6 +317,9 @@ int pem_read_buffer( pem_context *ctx, const char *header, const char *footer,
           ( POLARSSL_AES_C || POLARSSL_DES_C ) */
     }
 
+    if( s1 == s2 )
+        return( POLARSSL_ERR_PEM_INVALID_DATA );
+
     len = 0;
     ret = base64_decode( NULL, &len, s1, s2 - s1 );