Index: clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h
===================================================================
--- clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h
+++ clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h
@@ -42,6 +42,10 @@
 // through the handler class.
 void checkUnsafeBufferUsage(const Decl *D, UnsafeBufferUsageHandler &Handler);
 
+// Tests if any two `FixItHint`s in `FixIts` conflict.  Two `FixItHint`s
+// conflict if they have overlapping source ranges.
+bool anyConflict(const SourceManager &SM, const llvm::SmallVectorImpl<FixItHint> &FixIts);
+
 /// The text indicating that the user needs to provide input there:
 constexpr static const char *const UserFillPlaceHolder = "...";
 } // end namespace clang
Index: clang/lib/Analysis/UnsafeBufferUsage.cpp
===================================================================
--- clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -109,7 +109,7 @@
 
 AST_MATCHER_P(Stmt, forEveryDescendant, internal::Matcher<Stmt>, innerMatcher) {
   const DynTypedMatcher &DTM = static_cast<DynTypedMatcher>(innerMatcher);
-  
+
   MatchDescendantVisitor Visitor(&DTM, Finder, Builder, ASTMatchFinder::BK_All);  
   return Visitor.findMatch(DynTypedNode::create(Node));
 }
@@ -690,6 +690,37 @@
   }
 }
 
+bool clang::anyConflict(const SourceManager &SM,
+                        const llvm::SmallVectorImpl<FixItHint> &FixIts) {
+  // A simple interval overlap detecting algorithm.  Sorts all ranges by their
+  // begin location then find any overlap in one pass.
+  std::vector<const FixItHint *> All; // a copy of `FixIts`
+
+  for (const FixItHint &H : FixIts)
+    All.push_back(&H);
+  std::sort(All.begin(), All.end(),
+            [&SM](const FixItHint *H1, const FixItHint *H2) {
+              return SM.isBeforeInTranslationUnit(H1->RemoveRange.getBegin(),
+                                                  H2->RemoveRange.getBegin());
+            });
+
+  const FixItHint *CurrHint = nullptr;
+
+  for (const FixItHint *Hint : All) {
+    if (!CurrHint ||
+        SM.isBeforeInTranslationUnit(CurrHint->RemoveRange.getEnd(),
+                                     Hint->RemoveRange.getBegin())) {
+      // Either to initialize `CurrHint` or `CurrHint` does not
+      // overlap with `Hint`:
+      CurrHint = Hint;
+    } else
+      // In case `Hint` overlaps the `CurrHint`, we found at least one
+      // conflict:
+      return true;
+  }
+  return false;
+}
+
 void clang::checkUnsafeBufferUsage(const Decl *D,
                                    UnsafeBufferUsageHandler &Handler) {
   assert(D && D->getBody());
@@ -777,9 +808,7 @@
           Fixes = std::nullopt;
           break;
         }
-
-        for (auto &&Fixit: *F)
-          Fixes->push_back(std::move(Fixit));
+        Fixes->insert(Fixes->end(), F->begin(), F->end());
       }
     }
 
@@ -789,7 +818,8 @@
       Fixes->insert(Fixes->end(), std::make_move_iterator(VarF.begin()),
                     std::make_move_iterator(VarF.end()));
       // If we reach this point, the strategy is applicable.
-      Handler.handleFixableVariable(VD, std::move(*Fixes));
+      if (!anyConflict(Ctx.getSourceManager(), *Fixes))
+        Handler.handleFixableVariable(VD, std::move(*Fixes));
     } else {
       // The strategy has failed. Emit the warning without the fixit.
       S.set(VD, Strategy::Kind::Wontfix);
Index: clang/unittests/Analysis/CMakeLists.txt
===================================================================
--- clang/unittests/Analysis/CMakeLists.txt
+++ clang/unittests/Analysis/CMakeLists.txt
@@ -9,6 +9,7 @@
   CloneDetectionTest.cpp
   ExprMutationAnalyzerTest.cpp
   MacroExpansionContextTest.cpp
+  UnsafeBufferUsageTest.cpp
   )
 
 clang_target_link_libraries(ClangAnalysisTests
Index: clang/unittests/Analysis/UnsafeBufferUsageTest.cpp
===================================================================
--- /dev/null
+++ clang/unittests/Analysis/UnsafeBufferUsageTest.cpp
@@ -0,0 +1,60 @@
+#include "gtest/gtest.h"
+#include "clang/Basic/SourceLocation.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Basic/Diagnostic.h"
+#include "clang/Basic/FileManager.h"
+#include "clang/Analysis/Analyses/UnsafeBufferUsage.h"
+
+using namespace clang;
+
+namespace {
+// The test fixture.
+class UnsafeBufferUsageTest : public ::testing::Test {
+protected:
+  UnsafeBufferUsageTest()
+      : FileMgr(FileMgrOpts), DiagID(new DiagnosticIDs()),
+        Diags(DiagID, new DiagnosticOptions, new IgnoringDiagConsumer()),
+        SourceMgr(Diags, FileMgr) {}
+
+  FileSystemOptions FileMgrOpts;
+  FileManager FileMgr;
+  IntrusiveRefCntPtr<DiagnosticIDs> DiagID;
+  DiagnosticsEngine Diags;
+  SourceManager SourceMgr;
+};
+} // namespace
+
+TEST_F(UnsafeBufferUsageTest, FixItHintsConflict) {
+  const FileEntry *DummyFile = FileMgr.getVirtualFile("<virtual>", 100, 0);
+  FileID DummyFileID = SourceMgr.getOrCreateFileID(DummyFile, SrcMgr::C_User);
+  SourceLocation StartLoc = SourceMgr.getLocForStartOfFile(DummyFileID);
+
+#define MkDummyHint(Begin, End)                                                \
+  FixItHint::CreateReplacement(SourceRange(StartLoc.getLocWithOffset((Begin)), \
+                                           StartLoc.getLocWithOffset((End))),  \
+                               "dummy")
+
+  FixItHint H1 = MkDummyHint(0, 5);
+  FixItHint H2 = MkDummyHint(6, 10);
+  FixItHint H3 = MkDummyHint(20, 25);
+  llvm::SmallVector<FixItHint> Fixes;
+
+  // Test non-overlapping fix-its:
+  Fixes = {H1, H2, H3};
+  EXPECT_FALSE(anyConflict(SourceMgr, Fixes));
+  Fixes = {H3, H2, H1}; // re-order
+  EXPECT_FALSE(anyConflict(SourceMgr, Fixes));
+
+  // Test overlapping fix-its:
+  Fixes = {H1, H2, H3, MkDummyHint(0, 4) /* included in H1 */};
+  EXPECT_TRUE(anyConflict(SourceMgr, Fixes));
+
+  Fixes = {H1, H2, H3, MkDummyHint(10, 15) /* overlaps H2 */};
+  EXPECT_TRUE(anyConflict(SourceMgr, Fixes));
+
+  Fixes = {H1, H2, H3, MkDummyHint(7, 23) /* overlaps H2, H3 */};
+  EXPECT_TRUE(anyConflict(SourceMgr, Fixes));
+
+  Fixes = {H1, H2, H3, MkDummyHint(2, 23) /* overlaps H1, H2, and H3 */};
+  EXPECT_TRUE(anyConflict(SourceMgr, Fixes));
+}
\ No newline at end of file