diff --git a/ChangeLog.d/issue4176.txt b/ChangeLog.d/issue4176.txt
new file mode 100644
index 0000000..ddca37f
--- /dev/null
+++ b/ChangeLog.d/issue4176.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix a resource leak in a test suite with an alternative AES
+     implementation. Fixes #4176.
diff --git a/ChangeLog.d/winsock.txt b/ChangeLog.d/winsock.txt
new file mode 100644
index 0000000..0b42e69
--- /dev/null
+++ b/ChangeLog.d/winsock.txt
@@ -0,0 +1,4 @@
+Bugfix
+   * Fix mbedtls_net_poll() and mbedtls_net_recv_timeout() often failing with
+     MBEDTLS_ERR_NET_POLL_FAILED on Windows. Fixes #4465.
+
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index fe33ac8..0abeb43 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -2237,7 +2237,7 @@
 #if defined(MBEDTLS_ECP_C)
 /**
  * \brief          Set the allowed curves in order of preference.
- *                 (Default: all defined curves.)
+ *                 (Default: all defined curves in order of decreasing size.)
  *
  *                 On server: this only affects selection of the ECDHE curve;
  *                 the curves used for ECDH and ECDSA are determined by the
@@ -2269,7 +2269,9 @@
 #if defined(MBEDTLS_KEY_EXCHANGE__WITH_CERT__ENABLED)
 /**
  * \brief          Set the allowed hashes for signatures during the handshake.
- *                 (Default: all available hashes except MD5.)
+ *                 (Default: all SHA-2 hashes, largest first. Also SHA-1 if
+ *                 the compile-time option
+ *                 `MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_KEY_EXCHANGE` is enabled.)
  *
  * \note           This only affects which hashes are offered and can be used
  *                 for signatures during the handshake. Hashes for message
diff --git a/include/mbedtls/x509_crt.h b/include/mbedtls/x509_crt.h
index c38e0c0..30da190 100644
--- a/include/mbedtls/x509_crt.h
+++ b/include/mbedtls/x509_crt.h
@@ -229,12 +229,21 @@
 /**
  * Default security profile. Should provide a good balance between security
  * and compatibility with current deployments.
+ *
+ * This profile permits:
+ * - SHA2 hashes.
+ * - All supported elliptic curves.
+ * - RSA with 2048 bits and above.
+ *
+ * New minor versions of Mbed TLS may extend this profile, for example if
+ * new curves are added to the library. New minor versions of Mbed TLS will
+ * not reduce this profile unless serious security concerns require it.
  */
 extern const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_default;
 
 /**
  * Expected next default profile. Recommended for new deployments.
- * Currently targets a 128-bit security level, except for RSA-2048.
+ * Currently targets a 128-bit security level, except for allowing RSA-2048.
  */
 extern const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_next;
 
diff --git a/library/net_sockets.c b/library/net_sockets.c
index 3874783..1e701a5 100644
--- a/library/net_sockets.c
+++ b/library/net_sockets.c
@@ -167,6 +167,31 @@
 }
 
 /*
+ * Return 0 if the file descriptor is valid, an error otherwise.
+ * If for_select != 0, check whether the file descriptor is within the range
+ * allowed for fd_set used for the FD_xxx macros and the select() function.
+ */
+static int check_fd( int fd, int for_select )
+{
+    if( fd < 0 )
+        return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
+
+#if (defined(_WIN32) || defined(_WIN32_WCE)) && !defined(EFIX64) && \
+    !defined(EFI32)
+    (void) for_select;
+#else
+    /* A limitation of select() is that it only works with file descriptors
+     * that are strictly less than FD_SETSIZE. This is a limitation of the
+     * fd_set type. Error out early, because attempting to call FD_SET on a
+     * large file descriptor is a buffer overflow on typical platforms. */
+    if( for_select && fd >= FD_SETSIZE )
+        return( MBEDTLS_ERR_NET_POLL_FAILED );
+#endif
+
+    return( 0 );
+}
+
+/*
  * Initialize a context
  */
 void mbedtls_net_init( mbedtls_net_context *ctx )
@@ -497,15 +522,9 @@
 
     int fd = ctx->fd;
 
-    if( fd < 0 )
-        return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
-
-    /* A limitation of select() is that it only works with file descriptors
-     * that are strictly less than FD_SETSIZE. This is a limitation of the
-     * fd_set type. Error out early, because attempting to call FD_SET on a
-     * large file descriptor is a buffer overflow on typical platforms. */
-    if( fd >= FD_SETSIZE )
-        return( MBEDTLS_ERR_NET_POLL_FAILED );
+    ret = check_fd( fd, 1 );
+    if( ret != 0 )
+        return( ret );
 
 #if defined(__has_feature)
 #if __has_feature(memory_sanitizer)
@@ -584,8 +603,9 @@
     int ret;
     int fd = ((mbedtls_net_context *) ctx)->fd;
 
-    if( fd < 0 )
-        return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
+    ret = check_fd( fd, 0 );
+    if( ret != 0 )
+        return( ret );
 
     ret = (int) read( fd, buf, len );
 
@@ -623,15 +643,9 @@
     fd_set read_fds;
     int fd = ((mbedtls_net_context *) ctx)->fd;
 
-    if( fd < 0 )
-        return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
-
-    /* A limitation of select() is that it only works with file descriptors
-     * that are strictly less than FD_SETSIZE. This is a limitation of the
-     * fd_set type. Error out early, because attempting to call FD_SET on a
-     * large file descriptor is a buffer overflow on typical platforms. */
-    if( fd >= FD_SETSIZE )
-        return( MBEDTLS_ERR_NET_POLL_FAILED );
+    ret = check_fd( fd, 1 );
+    if( ret != 0 )
+        return( ret );
 
     FD_ZERO( &read_fds );
     FD_SET( fd, &read_fds );
@@ -671,8 +685,9 @@
     int ret;
     int fd = ((mbedtls_net_context *) ctx)->fd;
 
-    if( fd < 0 )
-        return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
+    ret = check_fd( fd, 0 );
+    if( ret != 0 )
+        return( ret );
 
     ret = (int) write( fd, buf, len );
 
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 4b53d1a..14c53fc 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -116,9 +116,8 @@
  */
 #define X509_MAX_VERIFY_CHAIN_SIZE    ( MBEDTLS_X509_MAX_INTERMEDIATE_CA + 2 )
 
-/*
- * Default profile
- */
+/* Default profile. Do not remove items unless there are serious security
+ * concerns. */
 const mbedtls_x509_crt_profile mbedtls_x509_crt_profile_default =
 {
 #if defined(MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_CERTIFICATES)
diff --git a/tests/suites/test_suite_aes.function b/tests/suites/test_suite_aes.function
index 23bf83d..1b7e5db 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -208,6 +208,8 @@
     /* Valid pointers are passed for builds with MBEDTLS_CHECK_PARAMS, as
      * otherwise we wouldn't get to the size check we're interested in. */
     TEST_ASSERT( mbedtls_aes_crypt_xts( &ctx, MBEDTLS_AES_ENCRYPT, length, data_unit, src, output ) == retval );
+exit:
+    mbedtls_aes_xts_free( &ctx );
 }
 /* END_CASE */