diff --git base/BUILD.gn base/BUILD.gn
index 80f6eaf01c022..b1a35ad087a5b 100644
--- base/BUILD.gn
+++ base/BUILD.gn
@@ -40,6 +40,7 @@ import("//build/config/ui.gni")
 import("//build/nocompile.gni")
 import("//build/timestamp.gni")
 import("//build_overrides/build.gni")
+import("//cef/libcef/features/features.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("//testing/test.gni")
 
@@ -1535,7 +1536,11 @@ component("base") {
     "hash/md5_constexpr_internal.h",
     "hash/sha1.h",
   ]
-  if (is_nacl) {
+  deps += [ "//cef/libcef/features" ]
+  if (enable_cef) {
+    configs += [ "//cef/libcef/features:config" ]
+  }
+  if (is_nacl || is_cef_sandbox_build) {
     sources += [
       "hash/md5_nacl.cc",
       "hash/md5_nacl.h",
@@ -1935,6 +1940,12 @@ component("base") {
       defines += [ "COM_INIT_CHECK_HOOK_DISABLED" ]
     }
 
+    if (!use_custom_libcxx) {
+      # Enable the VS 2015 Update 2 fix when building with the MSVC standard
+      # library.
+      defines += [ "_ENABLE_ATOMIC_ALIGNMENT_FIX" ]
+    }
+
     libs += [
       "cfgmgr32.lib",
       "ntdll.lib",
diff --git base/allocator/dispatcher/dispatcher.cc base/allocator/dispatcher/dispatcher.cc
index 0f044388cefee..49fc4cd20be64 100644
--- base/allocator/dispatcher/dispatcher.cc
+++ base/allocator/dispatcher/dispatcher.cc
@@ -13,6 +13,7 @@
 #include "base/dcheck_is_on.h"
 #include "base/no_destructor.h"
 #include "base/sampling_heap_profiler/poisson_allocation_sampler.h"
+#include "cef/libcef/features/features.h"
 
 #if DCHECK_IS_ON()
 #include <atomic>
@@ -259,7 +260,7 @@ struct Dispatcher::Impl {
   }
 
   void Reset() {
-#if DCHECK_IS_ON()
+#if DCHECK_IS_ON() && !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
     DCHECK([&]() {
       auto const was_set = is_initialized_check_flag_.test_and_set();
       is_initialized_check_flag_.clear();
diff --git base/hash/md5.h base/hash/md5.h
index aa889f350e8f7..50acac8a69225 100644
--- base/hash/md5.h
+++ base/hash/md5.h
@@ -10,8 +10,9 @@
 #include "base/base_export.h"
 #include "base/strings/string_piece.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/features.h"
 
-#if BUILDFLAG(IS_NACL)
+#if BUILDFLAG(IS_NACL) || BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "base/hash/md5_nacl.h"
 #else
 #include "base/hash/md5_boringssl.h"
diff --git base/hash/sha1.h base/hash/sha1.h
index 29626e5853c6e..2fb1c61504c5d 100644
--- base/hash/sha1.h
+++ base/hash/sha1.h
@@ -14,7 +14,9 @@
 #include "base/containers/span.h"
 #include "base/strings/string_piece.h"
 #include "build/build_config.h"
-#if BUILDFLAG(IS_NACL)
+#include "cef/libcef/features/features.h"
+
+#if BUILDFLAG(IS_NACL) || BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "base/hash/sha1_nacl.h"
 #else
 #include "base/hash/sha1_boringssl.h"
diff --git base/rand_util.h base/rand_util.h
index 04024537ee698..59864cb084559 100644
--- base/rand_util.h
+++ base/rand_util.h
@@ -15,8 +15,9 @@
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/features.h"
 
-#if !BUILDFLAG(IS_NACL)
+#if !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "third_party/boringssl/src/include/openssl/rand.h"
 #endif
 
@@ -93,7 +94,7 @@ class RandomBitGenerator {
   ~RandomBitGenerator() = default;
 };
 
-#if !BUILDFLAG(IS_NACL)
+#if !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 class NonAllocatingRandomBitGenerator {
  public:
   using result_type = uint64_t;
diff --git base/rand_util_win.cc base/rand_util_win.cc
index 2d9a1633b564f..d304c204c43ff 100644
--- base/rand_util_win.cc
+++ base/rand_util_win.cc
@@ -21,14 +21,19 @@
 #include <limits>
 
 #include "base/check.h"
+#include "cef/libcef/features/features.h"
+
+#if !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "base/feature_list.h"
 #include "third_party/boringssl/src/include/openssl/crypto.h"
 #include "third_party/boringssl/src/include/openssl/rand.h"
+#endif
 
 namespace base {
 
 namespace internal {
 
+#if !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 namespace {
 
 // The BoringSSl helpers are duplicated in rand_util_fuchsia.cc and
@@ -50,11 +55,16 @@ bool UseBoringSSLForRandBytes() {
   return g_use_boringssl.load(std::memory_order_relaxed);
 }
 
+#else  // !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
+void ConfigureBoringSSLBackedRandBytesFieldTrial() {}
+#endif
+
 }  // namespace internal
 
 namespace {
 
 void RandBytes(void* output, size_t output_length, bool avoid_allocation) {
+#if !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
   if (!avoid_allocation && internal::UseBoringSSLForRandBytes()) {
     // Ensure BoringSSL is initialized so it can use things like RDRAND.
     CRYPTO_library_init();
@@ -62,6 +72,7 @@ void RandBytes(void* output, size_t output_length, bool avoid_allocation) {
     (void)RAND_bytes(static_cast<uint8_t*>(output), output_length);
     return;
   }
+#endif  // !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 
   char* output_ptr = static_cast<char*>(output);
   while (output_length > 0) {
diff --git base/unguessable_token.cc base/unguessable_token.cc
index aa7423f88d278..1b2c7d3e3c4a0 100644
--- base/unguessable_token.cc
+++ base/unguessable_token.cc
@@ -10,8 +10,9 @@
 #include "base/format_macros.h"
 #include "base/rand_util.h"
 #include "build/build_config.h"
+#include "cef/libcef/features/features.h"
 
-#if !BUILDFLAG(IS_NACL)
+#if !BUILDFLAG(IS_NACL) && !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "third_party/boringssl/src/include/openssl/mem.h"
 #endif
 
@@ -46,7 +47,7 @@ absl::optional<UnguessableToken> UnguessableToken::Deserialize(uint64_t high,
 }
 
 bool UnguessableToken::operator==(const UnguessableToken& other) const {
-#if BUILDFLAG(IS_NACL)
+#if BUILDFLAG(IS_NACL) || BUILDFLAG(IS_CEF_SANDBOX_BUILD)
   // BoringSSL is unavailable for NaCl builds so it remains timing dependent.
   return token_ == other.token_;
 #else
diff --git base/win/sid.cc base/win/sid.cc
index 0f1a2ec79aa4b..7f92778a4a776 100644
--- base/win/sid.cc
+++ base/win/sid.cc
@@ -15,6 +15,7 @@
 #include <utility>
 
 #include "base/check.h"
+#include "base/notreached.h"
 #include "base/no_destructor.h"
 #include "base/rand_util.h"
 #include "base/ranges/algorithm.h"
@@ -22,8 +23,12 @@
 #include "base/win/scoped_handle.h"
 #include "base/win/scoped_localalloc.h"
 #include "base/win/windows_version.h"
+#include "cef/libcef/features/features.h"
+
+#if !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
 #include "third_party/boringssl/src/include/openssl/crypto.h"
 #include "third_party/boringssl/src/include/openssl/sha.h"
+#endif
 
 namespace base::win {
 
@@ -124,6 +129,7 @@ Sid Sid::FromNamedCapability(const std::wstring& capability_name) {
   if (known_cap != known_capabilities->end()) {
     return FromKnownCapability(known_cap->second);
   }
+#if !BUILDFLAG(IS_CEF_SANDBOX_BUILD)
   CRYPTO_library_init();
   static_assert((SHA256_DIGEST_LENGTH / sizeof(DWORD)) ==
                 SECURITY_APP_PACKAGE_RID_COUNT);
@@ -136,6 +142,10 @@ Sid Sid::FromNamedCapability(const std::wstring& capability_name) {
          reinterpret_cast<uint8_t*>(&rids[2]));
   return FromSubAuthorities(SECURITY_APP_PACKAGE_AUTHORITY, std::size(rids),
                             rids);
+#else
+  NOTREACHED();
+  return Sid(WellKnownSid::kNull);
+#endif
 }
 
 Sid Sid::FromKnownSid(WellKnownSid type) {