diff --git a/ChangeLog b/ChangeLog
index f6d3124..bc2a7c8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -17,6 +17,11 @@
 
 Bugfix
    * Fix an unchecked call to mbedtls_md() in the x509write module.
+   * Fix a bug in mbedtls_pk_parse_key() that would cause it to accept some
+     RSA keys that would later be rejected by functions expecting private
+     keys. Found by Catena cyber using oss-fuzz (issue 20467).
+   * Fix a bug in mbedtls_pk_parse_key() that would cause it to accept some
+     RSA keys with invalid values by silently fixing those values.
 
 = mbed TLS 2.16.4 branch released 2020-01-15
 
diff --git a/library/pkparse.c b/library/pkparse.c
index 0ae2402..d500457 100644
--- a/library/pkparse.c
+++ b/library/pkparse.c
@@ -678,6 +678,32 @@
 
 #if defined(MBEDTLS_RSA_C)
 /*
+ * Wrapper around mbedtls_asn1_get_mpi() that rejects zero.
+ *
+ * The value zero is:
+ * - never a valid value for an RSA parameter
+ * - interpreted as "omitted, please reconstruct" by mbedtls_rsa_complete().
+ *
+ * Since values can't be omitted in PKCS#1, passing a zero value to
+ * rsa_complete() would be incorrect, so reject zero values early.
+ */
+static int asn1_get_nonzero_mpi( unsigned char **p,
+                                 const unsigned char *end,
+                                 mbedtls_mpi *X )
+{
+    int ret;
+
+    ret = mbedtls_asn1_get_mpi( p, end, X );
+    if( ret != 0 )
+        return( ret );
+
+    if( mbedtls_mpi_cmp_int( X, 0 ) == 0 )
+        return( MBEDTLS_ERR_PK_KEY_INVALID_FORMAT );
+
+    return( 0 );
+}
+
+/*
  * Parse a PKCS#1 encoded private RSA key
  */
 static int pk_parse_key_pkcs1_der( mbedtls_rsa_context *rsa,
@@ -729,46 +755,36 @@
     }
 
     /* Import N */
-    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
-                                      MBEDTLS_ASN1_INTEGER ) ) != 0 ||
-        ( ret = mbedtls_rsa_import_raw( rsa, p, len, NULL, 0, NULL, 0,
-                                        NULL, 0, NULL, 0 ) ) != 0 )
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_rsa_import( rsa, &T, NULL, NULL,
+                                        NULL, NULL ) ) != 0 )
         goto cleanup;
-    p += len;
 
     /* Import E */
-    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
-                                      MBEDTLS_ASN1_INTEGER ) ) != 0 ||
-        ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, NULL, 0,
-                                        NULL, 0, p, len ) ) != 0 )
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_rsa_import( rsa, NULL, NULL, NULL,
+                                        NULL, &T ) ) != 0 )
         goto cleanup;
-    p += len;
 
     /* Import D */
-    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
-                                      MBEDTLS_ASN1_INTEGER ) ) != 0 ||
-        ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, NULL, 0,
-                                        p, len, NULL, 0 ) ) != 0 )
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_rsa_import( rsa, NULL, NULL, NULL,
+                                        &T, NULL ) ) != 0 )
         goto cleanup;
-    p += len;
 
     /* Import P */
-    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
-                                      MBEDTLS_ASN1_INTEGER ) ) != 0 ||
-        ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, p, len, NULL, 0,
-                                        NULL, 0, NULL, 0 ) ) != 0 )
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_rsa_import( rsa, NULL, &T, NULL,
+                                        NULL, NULL ) ) != 0 )
         goto cleanup;
-    p += len;
 
     /* Import Q */
-    if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
-                                      MBEDTLS_ASN1_INTEGER ) ) != 0 ||
-        ( ret = mbedtls_rsa_import_raw( rsa, NULL, 0, NULL, 0, p, len,
-                                        NULL, 0, NULL, 0 ) ) != 0 )
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_rsa_import( rsa, NULL, NULL, &T,
+                                        NULL, NULL ) ) != 0 )
         goto cleanup;
-    p += len;
 
-#if !defined(MBEDTLS_RSA_NO_CRT)
+#if !defined(MBEDTLS_RSA_NO_CRT) && !defined(MBEDTLS_RSA_ALT)
     /*
     * The RSA CRT parameters DP, DQ and QP are nominally redundant, in
     * that they can be easily recomputed from D, P and Q. However by
@@ -781,28 +797,42 @@
     */
 
     /* Import DP */
-    if( ( ret = mbedtls_asn1_get_mpi( &p, end, &rsa->DP ) ) != 0)
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_mpi_copy( &rsa->DP, &T ) ) != 0 )
        goto cleanup;
 
     /* Import DQ */
-    if( ( ret = mbedtls_asn1_get_mpi( &p, end, &rsa->DQ ) ) != 0)
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_mpi_copy( &rsa->DQ, &T ) ) != 0 )
        goto cleanup;
 
     /* Import QP */
-    if( ( ret = mbedtls_asn1_get_mpi( &p, end, &rsa->QP ) ) != 0)
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = mbedtls_mpi_copy( &rsa->QP, &T ) ) != 0 )
        goto cleanup;
 
 #else
     /* Verify existance of the CRT params */
-    if( ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 ||
-        ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 ||
-        ( ret = mbedtls_asn1_get_mpi( &p, end, &T ) ) != 0 )
+    if( ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 ||
+        ( ret = asn1_get_nonzero_mpi( &p, end, &T ) ) != 0 )
        goto cleanup;
 #endif
 
-    /* Complete the RSA private key */
-    if( ( ret = mbedtls_rsa_complete( rsa ) ) != 0 )
+    /* rsa_complete() doesn't complete anything with the default
+     * implementation but is still called:
+     * - for the benefit of alternative implementation that may want to
+     *   pre-compute stuff beyond what's provided (eg Montgomery factors)
+     * - as is also sanity-checks the key
+     *
+     * Furthermore, we also check the public part for consistency with
+     * mbedtls_pk_parse_pubkey(), as it includes size minima for example.
+     */
+    if( ( ret = mbedtls_rsa_complete( rsa ) ) != 0 ||
+        ( ret = mbedtls_rsa_check_pubkey( rsa ) ) != 0 )
+    {
         goto cleanup;
+    }
 
     if( p != end )
     {
diff --git a/tests/suites/test_suite_pkparse.data b/tests/suites/test_suite_pkparse.data
index 4add252..cd842cf 100644
--- a/tests/suites/test_suite_pkparse.data
+++ b/tests/suites/test_suite_pkparse.data
@@ -1072,33 +1072,84 @@
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256K1_ENABLED:MBEDTLS_PK_PARSE_EC_EXTENDED
 pk_parse_keyfile_ec:"data_files/ec_prv.specdom.der":"NULL":0
 
-Key ASN1 (Incorrect first tag)
-pk_parse_key:"":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+Key ASN1 (No data)
+pk_parse_key:"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (First tag not Sequence)
+pk_parse_key:"020100":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
 
 Key ASN1 (RSAPrivateKey, incorrect version tag)
 depends_on:MBEDTLS_RSA_C
-pk_parse_key:"300100":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"300100":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
 
 Key ASN1 (RSAPrivateKey, version tag missing)
 depends_on:MBEDTLS_RSA_C
-pk_parse_key:"3000":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"3000":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
 
 Key ASN1 (RSAPrivateKey, invalid version)
 depends_on:MBEDTLS_RSA_C
-pk_parse_key:"3003020101":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"3003020101":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
 
 Key ASN1 (RSAPrivateKey, correct version, incorrect tag)
 depends_on:MBEDTLS_RSA_C
-pk_parse_key:"300402010000":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"300402010000":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
 
-Key ASN1 (RSAPrivateKey, values present, length mismatch)
+Key ASN1 (RSAPrivateKey, correct format+values, minimal modulus size (128 bit))
 depends_on:MBEDTLS_RSA_C
-pk_parse_key:"301c02010002010102010102010102010102010102010102010102010100":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":0
 
-Key ASN1 (RSAPrivateKey, values present, check_privkey fails)
+Key ASN1 (RSAPrivateKey, correct format, modulus too small (127 bit))
 depends_on:MBEDTLS_RSA_C
-pk_parse_key:"301b020100020102020101020101020101020101020101020101020101":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"30630201000211007c8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct format, modulus even)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857002030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct format, d == 0)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"30630201000211007c8ab070369ede72920e5a51523c8571020301000102110000000000000000000000000000000000020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct format, d == p == q == 0)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c8571020301000102110000000000000000000000000000000000020900000000000000000002090000000000000000000209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, trailing garbage)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3064020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c00":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, n wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100FF1100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, e wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c8571FF030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, d wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c85710203010001FF11009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, p wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201FF0900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, q wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61FF0900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, dp wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a211FF09009471f14c26428401020813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, dq wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401FF0813425f060c4b72210208052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+
+Key ASN1 (RSAPrivateKey, correct values, qp wrong tag)
+depends_on:MBEDTLS_RSA_C
+pk_parse_key:"3063020100021100cc8ab070369ede72920e5a51523c857102030100010211009a6318982a7231de1894c54aa4909201020900f3058fd8dc484d61020900d7770dbd8b78a2110209009471f14c26428401020813425f060c4b7221FF08052b93d01747a87c":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
 
 Key ASN1 (ECPrivateKey, empty parameters)
 depends_on:MBEDTLS_ECP_C
-pk_parse_key:"30070201010400a000":"":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
+pk_parse_key:"30070201010400a000":MBEDTLS_ERR_PK_KEY_INVALID_FORMAT
diff --git a/tests/suites/test_suite_pkparse.function b/tests/suites/test_suite_pkparse.function
index 3eb0397..4650d33 100644
--- a/tests/suites/test_suite_pkparse.function
+++ b/tests/suites/test_suite_pkparse.function
@@ -113,23 +113,14 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE depends_on:MBEDTLS_RSA_C */
-void pk_parse_key( data_t * buf, char * result_str, int result )
+/* BEGIN_CASE */
+void pk_parse_key( data_t * buf, int result )
 {
     mbedtls_pk_context pk;
-    unsigned char output[2000];
-    ((void) result_str);
 
     mbedtls_pk_init( &pk );
 
-    memset( output, 0, 2000 );
-
-
-    TEST_ASSERT( mbedtls_pk_parse_key( &pk, buf->x, buf->len, NULL, 0 ) == ( result ) );
-    if( ( result ) == 0 )
-    {
-        TEST_ASSERT( 1 );
-    }
+    TEST_ASSERT( mbedtls_pk_parse_key( &pk, buf->x, buf->len, NULL, 0 ) == result );
 
 exit:
     mbedtls_pk_free( &pk );