diff --git a/3rdparty/CMakeLists.txt b/3rdparty/CMakeLists.txt
index 14a467457..fa149bdec 100644
--- a/3rdparty/CMakeLists.txt
+++ b/3rdparty/CMakeLists.txt
@@ -1,10 +1,2 @@
-execute_process(COMMAND ${MBEDTLS_PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../scripts/config.py -f ${CMAKE_CURRENT_SOURCE_DIR}/../include/mbedtls/mbedtls_config.h get MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED RESULT_VARIABLE everest_result)
-execute_process(COMMAND ${MBEDTLS_PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/../scripts/config.py -f ${CMAKE_CURRENT_SOURCE_DIR}/../include/mbedtls/mbedtls_config.h get MBEDTLS_PSA_P256M_DRIVER_ENABLED RESULT_VARIABLE p256m_result)
-
-if(${everest_result} EQUAL 0)
-    add_subdirectory(everest)
-endif()
-
-if(${p256m_result} EQUAL 0)
-    add_subdirectory(p256-m)
-endif()
+add_subdirectory(everest)
+add_subdirectory(p256-m)
diff --git a/ChangeLog.d/fix-cmake-3rdparty-custom-config.txt b/ChangeLog.d/fix-cmake-3rdparty-custom-config.txt
new file mode 100644
index 000000000..ec543aafc
--- /dev/null
+++ b/ChangeLog.d/fix-cmake-3rdparty-custom-config.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix the build with CMake when Everest or P256-m is enabled through
+     a user configuration file or the compiler command line. Fixes #8165.