diff --git a/ChangeLog b/ChangeLog
index 13cda1a60..0d9c93f89 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -6,6 +6,25 @@ Security
    * Fix possible heap buffer overflow in SSL if a very long hostname is used.
      Can be trigerred remotely if you accept hostnames from untrusted parties.
      Found by Guido Vranken.
+   * Fix stack buffer overflow in pkcs12 decryption (used by
+     mbedtls_pk_parse_key(file)() when the password is > 129 bytes.
+     Found by Guido Vranken. Not triggerable remotely.
+   * Fix potential buffer overflow in mbedtls_mpi_read_string().
+     Found by Guido Vranken. Not exploitable remotely in the context of TLS,
+     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 and fix provided by Guido Vranken.
+     Not triggerable remotely in TLS. Triggerable remotely if you accept PEM
+     data from an untrusted source.
+   * Fix possible heap buffer overflow in base64_encode() when the input
+     buffer is 512MB or larger on 32-bit platforms.
+     Found by Guido Vranken. Not trigerrable remotely in TLS.
+   * Fix potential heap buffer overflow in servers that perform client
+     authentication against a crafted CA cert. Cannot be triggered remotely
+     unless you allow third parties to pick trust CAs for client auth.
+     Found by Guido Vranken.
 
 Changes
    * ssl_set_hostname() now rejects host names longer that 255 bytes (maximum
diff --git a/include/polarssl/base64.h b/include/polarssl/base64.h
index db95cb1de..32634f8c9 100644
--- a/include/polarssl/base64.h
+++ b/include/polarssl/base64.h
@@ -44,6 +44,8 @@ extern "C" {
  * \return         0 if successful, or POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL.
  *                 *dlen is always updated to reflect the amount
  *                 of data that has (or would have) been written.
+ *                 If that length cannot be represented, then no data is
+ *                 written to the buffer and *dlen is set to SIZE_T_MAX.
  *
  * \note           Call this function with *dlen = 0 to obtain the
  *                 required buffer size in *dlen
diff --git a/library/base64.c b/library/base64.c
index c94995b9e..2b43a940a 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -61,6 +61,8 @@ static const unsigned char base64_dec_map[128] =
      49,  50,  51, 127, 127, 127, 127, 127
 };
 
+#define BASE64_SIZE_T_MAX   ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
+
 /*
  * Encode a buffer into base64 format
  */
@@ -77,15 +79,16 @@ int base64_encode( unsigned char *dst, size_t *dlen,
         return( 0 );
     }
 
-    n = (slen << 3) / 6;
+    n = slen / 3 + ( slen % 3 != 0 );
 
-    switch( (slen << 3) - (n * 6) )
+    if( n > ( BASE64_SIZE_T_MAX - 1 ) / 4 )
     {
-        case  2: n += 3; break;
-        case  4: n += 2; break;
-        default: break;
+        *dlen = BASE64_SIZE_T_MAX;
+        return( POLARSSL_ERR_BASE64_BUFFER_TOO_SMALL );
     }
 
+    n *= 4;
+
     if( *dlen < n + 1 )
     {
         *dlen = n + 1;
@@ -176,7 +179,10 @@ 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/bignum.c b/library/bignum.c
index bbadd01ce..14a3dc7cf 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -45,11 +45,14 @@ static void polarssl_zeroize( void *v, size_t n ) {
 #define biL    (ciL << 3)               /* bits  in limb  */
 #define biH    (ciL << 2)               /* half limb size */
 
+#define MPI_SIZE_T_MAX  ( (size_t) -1 ) /* SIZE_T_MAX is not standard */
+
 /*
  * Convert between bits/chars and number of limbs
+ * Divide first in order to avoid potential overflows
  */
-#define BITS_TO_LIMBS(i)  (((i) + biL - 1) / biL)
-#define CHARS_TO_LIMBS(i) (((i) + ciL - 1) / ciL)
+#define BITS_TO_LIMBS(i)  ( (i) / biL + ( (i) % biL != 0 ) )
+#define CHARS_TO_LIMBS(i) ( (i) / ciL + ( (i) % ciL != 0 ) )
 
 /*
  * Initialize one MPI
@@ -287,6 +290,9 @@ int mpi_read_string( mpi *X, int radix, const char *s )
 
     if( radix == 16 )
     {
+        if( slen > MPI_SIZE_T_MAX >> 2 )
+            return( POLARSSL_ERR_MPI_BAD_INPUT_DATA );
+
         n = BITS_TO_LIMBS( slen << 2 );
 
         MPI_CHK( mpi_grow( X, n ) );
diff --git a/library/pem.c b/library/pem.c
index 5c973ac25..81098eea5 100644
--- a/library/pem.c
+++ b/library/pem.c
@@ -287,6 +287,9 @@ int pem_read_buffer( pem_context *ctx, char *header, char *footer, const unsigne
 #endif /* POLARSSL_MD5_C && (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 );
 
diff --git a/library/pkcs12.c b/library/pkcs12.c
index 8e42d2035..498a3febd 100644
--- a/library/pkcs12.c
+++ b/library/pkcs12.c
@@ -80,6 +80,8 @@ static int pkcs12_parse_pbe_params( unsigned char **p,
     return( 0 );
 }
 
+#define PKCS12_MAX_PWDLEN 128
+
 static int pkcs12_pbe_derive_key_iv( asn1_buf *pbe_params, md_type_t md_type,
                                      const unsigned char *pwd,  size_t pwdlen,
                                      unsigned char *key, size_t keylen,
@@ -89,7 +91,10 @@ static int pkcs12_pbe_derive_key_iv( asn1_buf *pbe_params, md_type_t md_type,
     asn1_buf salt;
     size_t i;
     unsigned char *p, *end;
-    unsigned char unipwd[258];
+    unsigned char unipwd[PKCS12_MAX_PWDLEN * 2 + 2];
+
+    if( pwdlen > PKCS12_MAX_PWDLEN )
+        return( POLARSSL_ERR_PKCS12_BAD_INPUT_DATA );
 
     memset(&salt, 0, sizeof(asn1_buf));
     memset(&unipwd, 0, sizeof(unipwd));
@@ -122,6 +127,8 @@ static int pkcs12_pbe_derive_key_iv( asn1_buf *pbe_params, md_type_t md_type,
     return( 0 );
 }
 
+#undef PKCS12_MAX_PWDLEN
+
 int pkcs12_pbe_sha1_rc4_128( asn1_buf *pbe_params, int mode,
                              const unsigned char *pwd,  size_t pwdlen,
                              const unsigned char *data, size_t len,
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index cd9802a15..2f4ae6925 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -923,6 +923,7 @@ static int ssl_write_certificate_request( ssl_context *ssl )
     size_t n = 0, dn_size, total_dn_size;
     unsigned char *buf, *p;
     const x509_cert *crt;
+    const unsigned char * const end = ssl->out_msg + SSL_MAX_CONTENT_LEN;
 
     SSL_DEBUG_MSG( 2, ( "=> write certificate request" ) );
 
@@ -987,10 +988,14 @@ static int ssl_write_certificate_request( ssl_context *ssl )
     total_dn_size = 0;
     while( crt != NULL && crt->version != 0)
     {
-        if( p - buf > 4096 )
-            break;
-
         dn_size = crt->subject_raw.len;
+
+        if( end < p || (size_t)( end - p ) < 2 + dn_size )
+        {
+            SSL_DEBUG_MSG( 1, ( "skipping CAs: buffer too short" ) );
+            break;
+        }
+
         *p++ = (unsigned char)( dn_size >> 8 );
         *p++ = (unsigned char)( dn_size      );
         memcpy( p, crt->subject_raw.p, dn_size );