diff --git a/haystack/nodes/preprocessor/preprocessor.py b/haystack/nodes/preprocessor/preprocessor.py
index 9dd21978ce..9d76909bda 100644
--- a/haystack/nodes/preprocessor/preprocessor.py
+++ b/haystack/nodes/preprocessor/preprocessor.py
@@ -28,6 +28,7 @@
 
 with LazyImport("Run 'pip install farm-haystack[preprocessing]' or 'pip install nltk'") as nltk_import:
     import nltk
+    from nltk.tokenize.punkt import PunktTokenizer
 
 iso639_to_nltk = {
     "ru": "russian",
@@ -120,10 +121,18 @@ def __init__(
             nltk.data.find("tokenizers/punkt")
         except LookupError:
             try:
-                nltk.download("punkt")
+                nltk.download("punkt_tab")
             except FileExistsError as error:
                 logger.debug("NLTK punkt tokenizer seems to be already downloaded. Error message: %s", error)
                 pass
+
+        if tokenizer_model_folder is not None:
+            warnings.warn(
+                "Custom NLTK tokenizers are no longer allowed. "
+                "The 'tokenizer_model_folder' parameter will be ignored. "
+                "Please use the built-in nltk tokenizers instead by specifying the `language` parameter."
+            )
+        self.tokenizer_model_folder = None
         self.clean_whitespace = clean_whitespace
         self.clean_header_footer = clean_header_footer
         self.clean_empty_lines = clean_empty_lines
@@ -134,7 +143,6 @@ def __init__(
         self.split_respect_sentence_boundary = split_respect_sentence_boundary
         self.tokenizer = tokenizer
         self.language = language
-        self.tokenizer_model_folder = tokenizer_model_folder
         self.print_log: Set[str] = set()
         self.id_hash_keys = id_hash_keys
         self.progress_bar = progress_bar
@@ -922,14 +930,14 @@ def _load_sentence_tokenizer(self, language_name: Optional[str]) -> "nltk.tokeni
 
         # Use a default NLTK model
         elif language_name is not None:
-            sentence_tokenizer = nltk.data.load(f"tokenizers/punkt/{language_name}.pickle")
+            sentence_tokenizer = PunktTokenizer(language_name)
         else:
             logger.error(
                 "PreProcessor couldn't find the default sentence tokenizer model for %s. "
                 " Using English instead. You may train your own model and use the 'tokenizer_model_folder' parameter.",
                 self.language,
             )
-            sentence_tokenizer = nltk.data.load("tokenizers/punkt/english.pickle")
+            sentence_tokenizer = PunktTokenizer()  # default english model
 
         return sentence_tokenizer
 
diff --git a/pyproject.toml b/pyproject.toml
index 42b8acda5a..5d99d923b4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -87,7 +87,7 @@ dependencies = [
 [project.optional-dependencies]
 inference = [
   "transformers[torch,sentencepiece]==4.39.3",
-  "sentence-transformers>=2.3.1",  # See haystack/nodes/retriever/_embedding_encoder.py, _SentenceTransformersEmbeddingEncoder
+  "sentence-transformers<=3.0.0,>=2.3.1",  # See haystack/nodes/retriever/_embedding_encoder.py, _SentenceTransformersEmbeddingEncoder
   "huggingface-hub>=0.5.0",
 ]
 elasticsearch = [
@@ -147,13 +147,13 @@ crawler = [
   "selenium>=4.11.0"
 ]
 preprocessing = [
-  "nltk",
+  "nltk>=3.9.1",
   "langdetect",  # for language classification
 ]
 file-conversion = [
   "azure-ai-formrecognizer>=3.2.0b2",  # Microsoft Azure's Form Recognizer service (text and table exctrator)
   "python-docx",
-  "python-pptx",
+  "python-pptx<=1.0",
   "tika",  # Apache Tika (text & metadata extractor)
   "beautifulsoup4",
   "markdown",
@@ -191,7 +191,7 @@ colab = [
 dev = [
   "pre-commit",
   # Type check
-  "mypy",
+  "mypy==1.10.0",
   # Test
   "pytest",
   "pytest-cov",
diff --git a/releasenotes/notes/upgrade-ntlk-1e94de2d6f5dd3b6.yaml b/releasenotes/notes/upgrade-ntlk-1e94de2d6f5dd3b6.yaml
new file mode 100644
index 0000000000..7aa7817cef
--- /dev/null
+++ b/releasenotes/notes/upgrade-ntlk-1e94de2d6f5dd3b6.yaml
@@ -0,0 +1,9 @@
+fixes:
+  - |
+    Upgrades ntlk to 3.9.1 as prior versions are affect by https://nvd.nist.gov/vuln/detail/CVE-2024-39705.
+upgrade:
+  - |
+    Upgrades ntlk to 3.9.1 as prior versions are affect by https://nvd.nist.gov/vuln/detail/CVE-2024-39705. Due to these security vulnerabilities, it is not possible to use custom NLTK tokenizer models with the new version (for example in PreProcessor). Users can still use built-in nltk tokenizers by specifying the language parameter in the PreProcessor. See PreProcessor documentation for more details.
+enhancements:
+  - |
+    Pins sentence-transformers<=3.0.0,>=2.3.1 and python-pptx<=1.0 to avoid some minor typing incompatibilities with the newer version of the respective libraries.
diff --git a/test/nodes/test_preprocessor.py b/test/nodes/test_preprocessor.py
index b719fe4a74..551e63f4e2 100644
--- a/test/nodes/test_preprocessor.py
+++ b/test/nodes/test_preprocessor.py
@@ -175,6 +175,7 @@ def test_preprocess_sentence_split_custom_models_non_default_language(split_leng
 
 @pytest.mark.unit
 @pytest.mark.parametrize("split_length_and_results", [(1, 8), (8, 1)])
+@pytest.mark.skip(reason="Skipped after upgrade to nltk 3.9, can't load this model pt anymore")
 def test_preprocess_sentence_split_custom_models(split_length_and_results, samples_path):
     split_length, expected_documents_count = split_length_and_results