diff --git a/llvm/CMakeLists.txt b/llvm/CMakeLists.txt
--- a/llvm/CMakeLists.txt
+++ b/llvm/CMakeLists.txt
@@ -487,6 +487,10 @@
 set(LLVM_USE_SANITIZER "" CACHE STRING
   "Define the sanitizer used to build binaries and tests.")
 option(LLVM_OPTIMIZE_SANITIZED_BUILDS "Pass -O1 on debug sanitizer builds" ON)
+set(LLVM_UBSAN_FLAGS
+    "-fsanitize=undefined -fno-sanitize=vptr,function -fno-sanitize-recover=all"
+    CACHE STRING
+    "Compile flags set to enable UBSan. Only used if LLVM_USE_SANITIZER contains 'Undefined'.")
 set(LLVM_LIB_FUZZING_ENGINE "" CACHE PATH
   "Path to fuzzing library for linking with fuzz targets")
 
diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -776,8 +776,7 @@
       endif()
     elseif (LLVM_USE_SANITIZER STREQUAL "Undefined")
       append_common_sanitizer_flags()
-      append("-fsanitize=undefined -fno-sanitize=vptr,function -fno-sanitize-recover=all"
-              CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      append("${LLVM_UBSAN_FLAGS}" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     elseif (LLVM_USE_SANITIZER STREQUAL "Thread")
       append_common_sanitizer_flags()
       append("-fsanitize=thread" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
@@ -786,8 +785,8 @@
     elseif (LLVM_USE_SANITIZER STREQUAL "Address;Undefined" OR
             LLVM_USE_SANITIZER STREQUAL "Undefined;Address")
       append_common_sanitizer_flags()
-      append("-fsanitize=address,undefined -fno-sanitize=vptr,function -fno-sanitize-recover=all"
-              CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      append("-fsanitize=address" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+      append("${LLVM_UBSAN_FLAGS}" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
     elseif (LLVM_USE_SANITIZER STREQUAL "Leaks")
       append_common_sanitizer_flags()
       append("-fsanitize=leak" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
diff --git a/llvm/docs/CMake.rst b/llvm/docs/CMake.rst
--- a/llvm/docs/CMake.rst
+++ b/llvm/docs/CMake.rst
@@ -428,6 +428,11 @@
   are ``Address``, ``Memory``, ``MemoryWithOrigins``, ``Undefined``, ``Thread``,
   ``DataFlow``, and ``Address;Undefined``. Defaults to empty string.
 
+**LLVM_UBSAN_FLAGS**:STRING
+  Defines the set of compile flags used to enable UBSan. Only used if
+  ``LLVM_USE_SANITIZER`` contains ``Undefined``. This can be used to override
+  the default set of UBSan flags.
+
 **LLVM_ENABLE_LTO**:STRING
   Add ``-flto`` or ``-flto=`` flags to the compile and link command
   lines, enabling link-time optimization. Possible values are ``Off``,