diff --git a/include/polarssl/config.h b/include/polarssl/config.h
index 2def1ee..6d7bd86 100644
--- a/include/polarssl/config.h
+++ b/include/polarssl/config.h
@@ -972,6 +972,19 @@
 #define POLARSSL_X509_CHECK_KEY_USAGE
 
 /**
+ * \def POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE
+ *
+ * Enable verification of the extendedKeyUsage extension (leaf certificates).
+ *
+ * Disabling this avoids problems with mis-issued and/or misused certificates.
+ *
+ * \warning Depending on your PKI use, disabling this can be a security risk!
+ *
+ * Comment to skip extendedKeyUsage checking for certificates.
+ */
+#define POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE
+
+/**
  * \def POLARSSL_ZLIB_SUPPORT
  *
  * If set, the SSL/TLS module uses ZLIB to support compression and
diff --git a/include/polarssl/x509_crt.h b/include/polarssl/x509_crt.h
index 93340ec..8e63381 100644
--- a/include/polarssl/x509_crt.h
+++ b/include/polarssl/x509_crt.h
@@ -264,6 +264,24 @@
 int x509_crt_check_key_usage( const x509_crt *crt, int usage );
 #endif /* POLARSSL_X509_CHECK_KEY_USAGE) */
 
+#if defined(POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE)
+/**
+ * \brief          Check usage of certificate against extentedJeyUsage.
+ *
+ * \param crt      Leaf certificate used.
+ * \param usage_oid Intended usage (eg OID_SERVER_AUTH or OID_CLIENT_AUTH).
+ * \param usage_len Length of usage_oid (eg given by OID_SIZE()).
+ *
+ * \return         0 is this use of the certificate is allowed,
+ *                 POLARSSL_ERR_X509_BAD_INPUT_DATA if not.
+ *
+ * \note           Usually only makes sense on leaf certificates.
+ */
+int x509_crt_check_extended_key_usage( const x509_crt *crt,
+                                       const char *usage_oid,
+                                       size_t usage_len );
+#endif /* POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE) */
+
 #if defined(POLARSSL_X509_CRL_PARSE_C)
 /**
  * \brief          Verify the certificate revocation status
diff --git a/library/x509_crt.c b/library/x509_crt.c
index 42fbfab..2c32122 100644
--- a/library/x509_crt.c
+++ b/library/x509_crt.c
@@ -1371,6 +1371,38 @@
 }
 #endif
 
+#if defined(POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE)
+int x509_crt_check_extended_key_usage( const x509_crt *crt,
+                                       const char *usage_oid,
+                                       size_t usage_len )
+{
+    const x509_sequence *cur;
+
+    /* Extension is not mandatory, absent means no restriction */
+    if( ( crt->ext_types & EXT_EXTENDED_KEY_USAGE ) == 0 )
+        return( 0 );
+
+    /*
+     * Look for the requested usage (or wildcard ANY) in our list
+     */
+    for( cur = &crt->ext_key_usage; cur != NULL; cur = cur->next )
+    {
+        const x509_buf *cur_oid = &cur->buf;
+
+        if( cur_oid->len == usage_len &&
+            memcmp( cur_oid->p, usage_oid, usage_len ) == 0 )
+        {
+            return( 0 );
+        }
+
+        if( OID_CMP( OID_ANY_EXTENDED_KEY_USAGE, cur_oid ) )
+            return( 0 );
+    }
+
+    return( POLARSSL_ERR_X509_BAD_INPUT_DATA );
+}
+#endif
+
 #if defined(POLARSSL_X509_CRL_PARSE_C)
 /*
  * Return 1 if the certificate is revoked, or 0 otherwise.
diff --git a/tests/data_files/server5.eku-cli.crt b/tests/data_files/server5.eku-cli.crt
new file mode 100644
index 0000000..8aa2e44
--- /dev/null
+++ b/tests/data_files/server5.eku-cli.crt
@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.eku-cs.crt b/tests/data_files/server5.eku-cs.crt
new file mode 100644
index 0000000..db97b40
--- /dev/null
+++ b/tests/data_files/server5.eku-cs.crt
@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.eku-cs_any.crt b/tests/data_files/server5.eku-cs_any.crt
new file mode 100644
index 0000000..8fa8632
--- /dev/null
+++ b/tests/data_files/server5.eku-cs_any.crt
@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.eku-srv.crt b/tests/data_files/server5.eku-srv.crt
new file mode 100644
index 0000000..64312f6
--- /dev/null
+++ b/tests/data_files/server5.eku-srv.crt
@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----
+MIIB5DCCAWmgAwIBAgIBPjAKBggqhkjOPQQDAjA+MQswCQYDVQQGEwJOTDERMA8G
+A1UEChMIUG9sYXJTU0wxHDAaBgNVBAMTE1BvbGFyc3NsIFRlc3QgRUMgQ0EwHhcN
+MTQwNDEwMTcyMTU0WhcNMjQwNDA3MTcyMTU0WjA0MQswCQYDVQQGEwJOTDERMA8G
+A1UEChMIUG9sYXJTU0wxEjAQBgNVBAMTCWxvY2FsaG9zdDBZMBMGByqGSM49AgEG
+CCqGSM49AwEHA0IABDfMVtl2CR5acj7HWS3/IG7ufPkGkXTQrRS192giWWKSTuUA
+2CMR/+ov0jRdXRa9iojCa3cNVc2KKg76Aci07f+jYjBgMAkGA1UdEwQCMAAwHQYD
+VR0OBBYEFFBhpY/UB9nXggEM5WV/jGNGpxO+MB8GA1UdIwQYMBaAFJ1tICRJAT8r
+y3i1Gbx+JMnb+zZ8MBMGA1UdJQQMMAoGCCsGAQUFBwMBMAoGCCqGSM49BAMCA2kA
+MGYCMQDQzjWB0xZs/8IsqJb7owYYtCiT17939Uuc/1yBF69pJRy7KV/qJlHNvlVu
+qwWVTx0CMQDNW/0dlX1gU6ashrZv5Ly4sijg/g645fFpfMKCNXysEb9xiBeEj5de
+2x5sX/0OSx4=
+-----END CERTIFICATE-----
diff --git a/tests/data_files/server5.eku-srv_cli.crt b/tests/data_files/server5.eku-srv_cli.crt
new file mode 100644
index 0000000..9f58fed
--- /dev/null
+++ b/tests/data_files/server5.eku-srv_cli.crt
@@ -0,0 +1,13 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
diff --git a/tests/suites/test_suite_x509parse.data b/tests/suites/test_suite_x509parse.data
index 8b1df44..fe3c6aa 100644
--- a/tests/suites/test_suite_x509parse.data
+++ b/tests/suites/test_suite_x509parse.data
@@ -871,3 +871,24 @@
 X509 crt keyUsage #8 (extension present, combined KU one absent)
 x509_check_key_usage:"data_files/server1.key_usage.crt":KU_KEY_ENCIPHERMENT|KU_KEY_AGREEMENT:POLARSSL_ERR_X509_BAD_INPUT_DATA
 
+X509 crt extendedKeyUsage #1 (no extension, serverAuth)
+x509_check_extended_key_usage:"data_files/server5.crt":"2B06010505070301":0
+
+X509 crt extendedKeyUsage #2 (single value, present)
+x509_check_extended_key_usage:"data_files/server5.eku-srv.crt":"2B06010505070301":0
+
+X509 crt extendedKeyUsage #3 (single value, absent)
+x509_check_extended_key_usage:"data_files/server5.eku-cli.crt":"2B06010505070301":POLARSSL_ERR_X509_BAD_INPUT_DATA
+
+X509 crt extendedKeyUsage #4 (two values, first)
+x509_check_extended_key_usage:"data_files/server5.eku-srv_cli.crt":"2B06010505070301":0
+
+X509 crt extendedKeyUsage #5 (two values, second)
+x509_check_extended_key_usage:"data_files/server5.eku-srv_cli.crt":"2B06010505070302":0
+
+X509 crt extendedKeyUsage #6 (two values, other)
+x509_check_extended_key_usage:"data_files/server5.eku-srv_cli.crt":"2B06010505070303":POLARSSL_ERR_X509_BAD_INPUT_DATA
+
+X509 crt extendedKeyUsage #7 (any, random)
+x509_check_extended_key_usage:"data_files/server5.eku-cs_any.crt":"2B060105050703FF":0
+
diff --git a/tests/suites/test_suite_x509parse.function b/tests/suites/test_suite_x509parse.function
index 4f64484..f3da1fc 100644
--- a/tests/suites/test_suite_x509parse.function
+++ b/tests/suites/test_suite_x509parse.function
@@ -331,6 +331,25 @@
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:POLARSSL_X509_CRT_PARSE_C:POLARSSL_X509_CHECK_EXTENDED_KEY_USAGE */
+void x509_check_extended_key_usage( char *crt_file, char *usage_hex, int ret )
+{
+    x509_crt crt;
+    char oid[50];
+    size_t len;
+
+    x509_crt_init( &crt );
+
+    len = unhexify( (unsigned char *) oid, usage_hex );
+
+    TEST_ASSERT( x509_crt_parse_file( &crt, crt_file ) == 0 );
+
+    TEST_ASSERT( x509_crt_check_extended_key_usage( &crt, oid, len ) == ret );
+
+    x509_crt_free( &crt );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:POLARSSL_X509_CRT_PARSE_C:POLARSSL_SELF_TEST */
 void x509_selftest()
 {