diff --git a/ChangeLog b/ChangeLog
index e57b5a441..5beeb3532 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -25,10 +25,11 @@ Changes
 
 Security
    * Forbid change of server certificate during renegotiation to prevent
-     "triple handshake" attack when authentication mode is optional (the
+     "triple handshake" attack when authentication mode is 'optional' (the
      attack was already impossible when authentication is required).
    * Check notBefore timestamp of certificates and CRLs from the future.
    * Forbid sequence number wrapping
+   * Fix possible buffer overflow with overlong PSK
 
 Bugfix
    * ecp_gen_keypair() does more tries to prevent failure because of
diff --git a/library/ssl_srv.c b/library/ssl_srv.c
index 85490502f..0241b43b7 100644
--- a/library/ssl_srv.c
+++ b/library/ssl_srv.c
@@ -2455,7 +2455,7 @@ static int ssl_parse_encrypted_pms( ssl_context *ssl,
 
     ret = pk_decrypt( ssl_own_key( ssl ), p, len,
                       pms, &ssl->handshake->pmslen,
-                      sizeof(ssl->handshake->premaster),
+                      sizeof( ssl->handshake->premaster ) - pms_offset,
                       ssl->f_rng, ssl->p_rng );
 
     if( ret != 0 || ssl->handshake->pmslen != 48 ||
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 3fd6e341a..8c6042858 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -916,6 +916,9 @@ int ssl_psk_derive_premaster( ssl_context *ssl, key_exchange_type_t key_ex )
     }
 
     /* opaque psk<0..2^16-1>; */
+    if( end - p < 2 + (int) ssl->psk_len )
+            return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
+
     *(p++) = (unsigned char)( ssl->psk_len >> 8 );
     *(p++) = (unsigned char)( ssl->psk_len      );
     memcpy( p, ssl->psk, ssl->psk_len );
@@ -3784,6 +3787,14 @@ int ssl_set_psk( ssl_context *ssl, const unsigned char *psk, size_t psk_len,
     if( psk == NULL || psk_identity == NULL )
         return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
 
+    /*
+     * The length will be check later anyway, but in case it is obviously
+     * too large, better abort now. The PMS is as follows:
+     * other_len (2 bytes) + other + psk_len (2 bytes) + psk
+     */
+    if( psk_len + 4 > POLARSSL_PREMASTER_SIZE )
+        return( POLARSSL_ERR_SSL_BAD_INPUT_DATA );
+
     if( ssl->psk != NULL )
     {
         polarssl_free( ssl->psk );