diff --git a/.circleci/continue_config_in.yml b/.circleci/continue_config_in.yml
index 329853f3..d2453612 100644
--- a/.circleci/continue_config_in.yml
+++ b/.circleci/continue_config_in.yml
@@ -48,16 +48,23 @@ jobs:
       image:
         default: PLACEHOLDER_IMAGE(gcc7_cmake3.9.5)
         type: string
+      sanitize:
+        default: "OFF"
+        type: string
     steps:
       - checkout
       - run: git submodule update --init --recursive
-      - run: cmake -D XLNT_ALL_WARNINGS_AS_ERRORS=<< parameters.warnings-as-errors >> -D XLNT_CXX_LANG=<< parameters.cxx-ver >> -D STATIC=<< parameters.static >> -D BENCHMARKS=<< parameters.benchmarks >> -D XLNT_MICROBENCH_ENABLED=<< parameters.micro-benchmarks >> -D TESTS=<< parameters.tests >> -D XLNT_SKIP_INTERNAL_TESTS=<< parameters.skip-internal-tests >> -D SAMPLES=<< parameters.samples >> -D COVERAGE=<< parameters.coverage >> -D CMAKE_BUILD_TYPE=<< parameters.build-type >> -D XLNT_USE_LOCALE_COMMA_DECIMAL_SEPARATOR=ON -D XLNT_LOCALE_COMMA_DECIMAL_SEPARATOR=de_DE -D XLNT_USE_LOCALE_ARABIC_DECIMAL_SEPARATOR=ON -D XLNT_LOCALE_ARABIC_DECIMAL_SEPARATOR=ps_AF .
+      - run: cmake -D XLNT_SANITIZE=<< parameters.sanitize >> -D XLNT_ALL_WARNINGS_AS_ERRORS=<< parameters.warnings-as-errors >> -D XLNT_CXX_LANG=<< parameters.cxx-ver >> -D STATIC=<< parameters.static >> -D BENCHMARKS=<< parameters.benchmarks >> -D XLNT_MICROBENCH_ENABLED=<< parameters.micro-benchmarks >> -D TESTS=<< parameters.tests >> -D XLNT_SKIP_INTERNAL_TESTS=<< parameters.skip-internal-tests >> -D SAMPLES=<< parameters.samples >> -D COVERAGE=<< parameters.coverage >> -D CMAKE_BUILD_TYPE=<< parameters.build-type >> -D XLNT_USE_LOCALE_COMMA_DECIMAL_SEPARATOR=ON -D XLNT_LOCALE_COMMA_DECIMAL_SEPARATOR=de_DE -D XLNT_USE_LOCALE_ARABIC_DECIMAL_SEPARATOR=ON -D XLNT_LOCALE_ARABIC_DECIMAL_SEPARATOR=ps_AF .
       - run: cmake --build . -- -j2
       - when:
           condition:
             equal: ["ON", << parameters.tests >>]
           steps:
-            - run: ./tests/xlnt.test
+            - run: |
+                if [ "<< parameters.sanitize >>" = "ON" ]; then
+                  export UBSAN_OPTIONS="suppressions=$PWD/ubsan.supp"
+                fi
+                ./tests/xlnt.test
       - when:
           condition:
             equal: ["ON", << parameters.samples >>]
@@ -175,6 +182,9 @@ jobs:
       cmake-generator:
         default: "Visual Studio 16 2019"
         type: string
+      sanitize:
+        default: "OFF"
+        type: string
     steps:
       - checkout
       - run: git submodule update --init --recursive
@@ -186,13 +196,103 @@ jobs:
           steps:
             - run: choco install visualstudio2017buildtools -y
             - run: choco install visualstudio2017-workload-vctools -y
-      - run: cmake -G "<< parameters.cmake-generator >>" -D CMAKE_GENERATOR_PLATFORM=x64 -D STATIC=<< parameters.static >> -D SAMPLES=<< parameters.samples >> -D BENCHMARKS=<< parameters.benchmarks >> -D TESTS=<< parameters.tests >> -D XLNT_SKIP_INTERNAL_TESTS=<< parameters.skip-internal-tests >> -D CMAKE_BUILD_TYPE=<< parameters.build-type >> .
+      - run: cmake -G "<< parameters.cmake-generator >>" -D XLNT_SANITIZE=<< parameters.sanitize >> -D CMAKE_GENERATOR_PLATFORM=x64 -D STATIC=<< parameters.static >> -D SAMPLES=<< parameters.samples >> -D BENCHMARKS=<< parameters.benchmarks >> -D TESTS=<< parameters.tests >> -D XLNT_SKIP_INTERNAL_TESTS=<< parameters.skip-internal-tests >> -D CMAKE_BUILD_TYPE=<< parameters.build-type >> .
       - run: cmake --build . -j4 --config << parameters.build-type >>
       - when:
           condition:
             equal: ["ON", << parameters.tests >>]
           steps:
-            - run: ./tests/<< parameters.build-type >>/xlnt.test.exe
+            - run: |
+                if [ "<< parameters.sanitize >>" = "ON" ]; then
+                  # CircleCI is using git bash on windows
+                  set -x
+
+                  ASAN_DIR=""
+
+                  #
+                  # 1) Preferred: use vswhere -find (robust across MSVC upgrades)
+                  #
+                  VSWHERE=""
+                  if [ -x "/c/Program Files (x86)/Microsoft Visual Studio/Installer/vswhere.exe" ]; then
+                    VSWHERE="/c/Program Files (x86)/Microsoft Visual Studio/Installer/vswhere.exe"
+                  elif [ -x "/c/Program Files/Microsoft Visual Studio/Installer/vswhere.exe" ]; then
+                    VSWHERE="/c/Program Files/Microsoft Visual Studio/Installer/vswhere.exe"
+                  fi
+
+                  if [ -n "$VSWHERE" ]; then
+                    # Try Hostx64/x64 first (typical for x64 builds)
+                    ASAN_DLL_WIN="$("$VSWHERE" -latest -products '*' \
+                      -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 \
+                      -find 'VC\Tools\MSVC\*\bin\Hostx64\x64\clang_rt.asan_dynamic-x86_64.dll' \
+                      | head -n 1 | tr -d '\r')"
+
+                    # Fallback to Hostx86/x64
+                    if [ -z "$ASAN_DLL_WIN" ]; then
+                      ASAN_DLL_WIN="$("$VSWHERE" -latest -products '*' \
+                        -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 \
+                        -find 'VC\Tools\MSVC\*\bin\Hostx86\x64\clang_rt.asan_dynamic-x86_64.dll' \
+                        | head -n 1 | tr -d '\r')"
+                    fi
+
+                    # If release DLL not found, try debug runtime DLL
+                    if [ -z "$ASAN_DLL_WIN" ]; then
+                      ASAN_DLL_WIN="$("$VSWHERE" -latest -products '*' \
+                        -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 \
+                        -find 'VC\Tools\MSVC\*\bin\Hostx64\x64\clang_rt.asan_dbg_dynamic-x86_64.dll' \
+                        | head -n 1 | tr -d '\r')"
+                    fi
+                    if [ -z "$ASAN_DLL_WIN" ]; then
+                      ASAN_DLL_WIN="$("$VSWHERE" -latest -products '*' \
+                        -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 \
+                        -find 'VC\Tools\MSVC\*\bin\Hostx86\x64\clang_rt.asan_dbg_dynamic-x86_64.dll' \
+                        | head -n 1 | tr -d '\r')"
+                    fi
+
+                    if [ -n "$ASAN_DLL_WIN" ]; then
+                      ASAN_DIR="$(dirname "$(cygpath -u "$ASAN_DLL_WIN")")"
+                    fi
+                  fi
+
+                  #
+                  # 2) Fallback: standard install directories + ls + GNU sort
+                  #
+                  if [ -z "$ASAN_DIR" ]; then
+                    for VSROOT in \
+                      "/c/Program Files (x86)/Microsoft Visual Studio/2019/Community" \
+                      "/c/Program Files (x86)/Microsoft Visual Studio/2019/BuildTools" \
+                      "/c/Program Files/Microsoft Visual Studio/2022/Community" \
+                      "/c/Program Files/Microsoft Visual Studio/2022/BuildTools"
+                    do
+                      if [ -d "$VSROOT/VC/Tools/MSVC" ]; then
+                        TOOLSET_BASE="$VSROOT/VC/Tools/MSVC"
+
+                        # Force GNU sort from Git Bash (avoid Windows sort.exe)
+                        MSVC_VER="$(ls -1 "$TOOLSET_BASE" | /usr/bin/sort -V | tail -n 1)"
+                        TOOLSET="$TOOLSET_BASE/$MSVC_VER"
+
+                        for d in "$TOOLSET/bin/Hostx64/x64" "$TOOLSET/bin/Hostx86/x64"; do
+                          if [ -f "$d/clang_rt.asan_dynamic-x86_64.dll" ] || [ -f "$d/clang_rt.asan_dbg_dynamic-x86_64.dll" ]; then
+                            ASAN_DIR="$d"
+                            break 2
+                          fi
+                        done
+                      fi
+                    done
+                  fi
+
+                  if [ -z "$ASAN_DIR" ]; then
+                    echo "ERROR: Could not locate MSVC ASan runtime DLL directory (clang_rt.asan_*_dynamic-x86_64.dll)." >&2
+                    exit 1
+                  fi
+
+                  export PATH="$ASAN_DIR:$PATH"
+                  echo "MSVC ASan runtime dir added to PATH: $ASAN_DIR"
+
+                  # Optional: validate via Windows loader search
+                  cmd.exe /c "where clang_rt.asan_dynamic-x86_64.dll" || true
+                fi
+
+                ./tests/<< parameters.build-type >>/xlnt.test.exe
       - when:
           condition:
             equal: ["ON", << parameters.samples >>]
@@ -224,13 +324,20 @@ jobs:
       static:
         default: "ON"
         type: string
+      sanitize:
+        default: "OFF"
+        type: string
     steps:
       - checkout
       - run: git submodule update --init --recursive
       - run: brew install cmake
-      - run: cmake -G "Xcode" -D STATIC=<< parameters.static >> -D SAMPLES=<< parameters.samples >> -D BENCHMARKS=<< parameters.benchmarks >> -D TESTS=ON -D CMAKE_BUILD_TYPE=<< parameters.build-type >> .
+      - run: cmake -G "Xcode" -D XLNT_SANITIZE=<< parameters.sanitize >> -D STATIC=<< parameters.static >> -D SAMPLES=<< parameters.samples >> -D BENCHMARKS=<< parameters.benchmarks >> -D TESTS=ON -D CMAKE_BUILD_TYPE=<< parameters.build-type >> .
       - run: cmake --build . -j6 --config << parameters.build-type >>
-      - run: ./tests/<< parameters.build-type >>/xlnt.test
+      - run: |
+          if [ "<< parameters.sanitize >>" = "ON" ]; then
+            export UBSAN_OPTIONS="suppressions=$PWD/ubsan.supp"
+          fi
+          ./tests/<< parameters.build-type >>/xlnt.test
       - when:
           condition:
             equal: ["ON", << parameters.samples >>]
@@ -297,6 +404,8 @@ workflows:
               - {static: "ON", skip-internal-tests: "ON", cxx-ver: "11", build-type: Release}
               - {static: "ON", skip-internal-tests: "ON", cxx-ver: "23", build-type: Debug}
               - {static: "ON", skip-internal-tests: "ON", cxx-ver: "23", build-type: Release}
+              # Exclude combination covered by tests-gcc-sanitize job
+              - {cxx-ver: "23", build-type: Debug, static: "OFF", skip-internal-tests: "OFF"}
           filters:
             branches:
               ignore: gh-pages
@@ -313,6 +422,26 @@ workflows:
             branches:
               ignore: gh-pages
 
+      - build-gcc:
+          name: tests-gcc-sanitize
+          image: PLACEHOLDER_IMAGE(gcc_cmake_latest)
+          matrix:
+            alias: tests-gcc-sanitize-all
+            parameters:
+              cxx-ver:
+                - "23"
+              build-type:
+                - Debug
+              static:
+                - "OFF"
+              skip-internal-tests:
+                - "OFF"
+              sanitize:
+                - "ON"
+          filters:
+            branches:
+              ignore: gh-pages
+
       - build-msvc:
           name: tests-samples-msvc
           matrix:
@@ -350,6 +479,20 @@ workflows:
             branches:
               ignore: gh-pages
 
+      - build-msvc:
+          name: tests-msvc-sanitize
+          build-type: Debug
+          static: "OFF"
+          skip-internal-tests: "OFF"
+          sanitize: "ON"
+          samples: "OFF"
+          benchmarks: "OFF"
+          requires:
+            - tests-gcc-sanitize-all # prevent building windows in case of gcc failures, as windows builds are more expensive
+          filters:
+            branches:
+              ignore: gh-pages
+
       - build-macos:
           name: tests-samples-macos
           matrix:
@@ -367,6 +510,18 @@ workflows:
             branches:
               ignore: gh-pages
 
+      - build-macos:
+          name: tests-macos-sanitize
+          build-type: Debug
+          static: "OFF"
+          samples: "OFF"
+          sanitize: "ON"
+          requires:
+            - tests-gcc-sanitize-all # prevent building macos in case of gcc failures, as macos builds are more expensive
+          filters:
+            branches:
+              ignore: gh-pages
+
       - docs-build:
           filters:
             branches:
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 72d0c18d..26135d69 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -46,9 +46,32 @@ option(TESTS "Set to ON to build test executable (in ./tests)" OFF)
 option(SAMPLES "Set to ON to build executable code samples (in ./samples)" OFF)
 option(BENCHMARKS "Set to ON to build performance benchmarks (in ./benchmarks)" OFF)
 option(PYTHON "Set to ON to build Arrow conversion functions (in ./python)" OFF)
+option(XLNT_SANITIZE "Sanitize addresses" OFF)
 mark_as_advanced(PYTHON)
 option(DOCUMENTATION "Set to ON to build API reference documentation (in ./api-reference)" OFF)
 
+if(XLNT_SANITIZE)
+    if(MSVC)
+        # Require VS 2019 16.9+ (cl with /fsanitize=address)
+        add_compile_options(/fsanitize=address /Zi)
+    else()
+        set(SANITIZER_FLAGS
+            -fno-omit-frame-pointer
+            -fsanitize=address
+            -fsanitize=undefined
+            -g
+        )
+
+        # LSan (leak sanitizer) is not supported on macOS with AppleClang
+        if (NOT (CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang"))
+            list(APPEND SANITIZER_FLAGS -fsanitize=leak)
+        endif()
+
+        add_compile_options(${SANITIZER_FLAGS})
+        add_link_options(${SANITIZER_FLAGS})
+    endif()
+endif()
+
 # Platform specific options
 if(MSVC)
   option(STATIC_CRT "Link with the static version of MSVCRT (/MT[d])" OFF)
diff --git a/source/detail/implementations/stylesheet.hpp b/source/detail/implementations/stylesheet.hpp
index 1d81566a..ebb8fa0c 100644
--- a/source/detail/implementations/stylesheet.hpp
+++ b/source/detail/implementations/stylesheet.hpp
@@ -569,6 +569,17 @@ struct stylesheet
         return !(*this == rhs);
     }
 
+    stylesheet() = default;
+    stylesheet(const stylesheet &) = default;
+    stylesheet(stylesheet &&) = default;
+    stylesheet &operator=(const stylesheet &) = default;
+    stylesheet &operator=(stylesheet &&) = default;
+
+    ~stylesheet() noexcept
+    {
+        garbage_collection_enabled = false;
+    }
+
     bool garbage_collection_enabled = true;
     bool known_fonts_enabled = false;
 
diff --git a/source/detail/serialization/xlsx_producer.cpp b/source/detail/serialization/xlsx_producer.cpp
index b9157be3..1cb366e7 100644
--- a/source/detail/serialization/xlsx_producer.cpp
+++ b/source/detail/serialization/xlsx_producer.cpp
@@ -92,6 +92,18 @@ xlsx_producer::xlsx_producer(const workbook &target)
 
 xlsx_producer::~xlsx_producer()
 {
+    if (current_cell_)
+    {
+        delete current_cell_;
+        current_cell_ = nullptr;
+    }
+
+    if (current_worksheet_)
+    {
+        delete current_worksheet_;
+        current_worksheet_ = nullptr;
+    }
+
     end_part();
     archive_.reset();
 }
diff --git a/ubsan.supp b/ubsan.supp
new file mode 100644
index 00000000..b8f0468a
--- /dev/null
+++ b/ubsan.supp
@@ -0,0 +1,7 @@
+# UBSan suppression file for xlnt
+# Usage: UBSAN_OPTIONS="suppressions=../ubsan.supp" ./tests/xlnt.test
+
+# Suppress null pointer arithmetic in expat (third-party library)
+# Bug: hashTableIterInit does `iter->end = iter->p + table->size` where iter->p can be NULL
+# This is technically UB but harmless in practice (NULL + 0 = NULL on all platforms)
+pointer-overflow:hashTableIterInit