diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c9e0e71..1e14f08b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.6.3] - 2026-05-??
+
+- Fix [#675](https://github.com/Neoteroi/BlackSheep/issues/675): fix `OverflowError`
+  when serving large files inefficiently; `get_chunks` in `scribe.pyx` used a C `int`
+  loop variable that overflows for responses larger than ~2 GB. Changed to `Py_ssize_t`.
+- Fix potential `OverflowError` in `cookies.pyx`: `Cookie.max_age` and the local
+  variable in `parse_cookie` were declared as C `int`; changed to `long long`.
+
 ## [2.6.2] - 2026-02-25 :gift:
 
 - Fix regression that broke compatibility with `Starlette` mounts
diff --git a/blacksheep/cookies.pxd b/blacksheep/cookies.pxd
index e981d16a..22d78b95 100644
--- a/blacksheep/cookies.pxd
+++ b/blacksheep/cookies.pxd
@@ -22,7 +22,7 @@ cdef class Cookie:
     cdef public str path
     cdef public bint http_only
     cdef public bint secure
-    cdef public int max_age
+    cdef public long long max_age
     cdef public CookieSameSiteMode same_site
     cpdef Cookie clone(self)
 
diff --git a/blacksheep/cookies.pyx b/blacksheep/cookies.pyx
index 2b4fb792..dbd7e905 100644
--- a/blacksheep/cookies.pyx
+++ b/blacksheep/cookies.pyx
@@ -40,7 +40,7 @@ cdef class Cookie:
         str path=None,
         bint http_only=0,
         bint secure=0,
-        int max_age=-1,
+        long long max_age=-1,
         CookieSameSiteMode same_site=CookieSameSiteMode.UNDEFINED
     ):
         self.name = name
@@ -126,7 +126,7 @@ cdef CookieSameSiteMode same_site_mode_from_bytes(bytes raw_value):
 
 cpdef Cookie parse_cookie(bytes raw_value):
     # https://tools.ietf.org/html/rfc6265
-    cdef int max_age
+    cdef long long max_age
     cdef bytes value = b''
     cdef bytes eq, expires, domain, path, part, k, v, lower_k, lower_part
     cdef bint http_only, secure
diff --git a/blacksheep/scribe.pyx b/blacksheep/scribe.pyx
index 935baaf4..80d96f16 100644
--- a/blacksheep/scribe.pyx
+++ b/blacksheep/scribe.pyx
@@ -7,7 +7,8 @@ from .messages cimport Request, Response
 from .url cimport URL
 
 
-cdef int MAX_RESPONSE_CHUNK_SIZE = 61440  # 64kb
+MAX_RESPONSE_CHUNK_SIZE = 61440  # 64kb — Python-accessible
+cdef int _MAX_RESPONSE_CHUNK_SIZE = MAX_RESPONSE_CHUNK_SIZE
 
 
 cdef bint should_use_chunked_encoding(Content content):
@@ -44,9 +45,9 @@ async def write_chunks(Content http_content):
 
 
 def get_chunks(bytes data):
-    cdef int i
-    for i in range(0, len(data), MAX_RESPONSE_CHUNK_SIZE):
-        yield data[i:i + MAX_RESPONSE_CHUNK_SIZE]
+    cdef Py_ssize_t i
+    for i in range(0, len(data), _MAX_RESPONSE_CHUNK_SIZE):
+        yield data[i:i + _MAX_RESPONSE_CHUNK_SIZE]
     yield b''
 
 
@@ -86,7 +87,7 @@ async def send_asgi_response(Response response, object send):
                     'more_body': False
                 })
         else:
-            if content.length > MAX_RESPONSE_CHUNK_SIZE:
+            if content.length > _MAX_RESPONSE_CHUNK_SIZE:
                 # Note: get_chunks yields the closing bytes fragment therefore
                 # we do not need to check for the closing message!
                 for chunk in get_chunks(content.body):
diff --git a/tests/test_cookies.py b/tests/test_cookies.py
index f82e960b..498ff3e6 100644
--- a/tests/test_cookies.py
+++ b/tests/test_cookies.py
@@ -395,3 +395,11 @@ def test_cookie_value_multibyte_within_limit():
     value = "ñ" * 1000
     cookie = Cookie("multibyte", value)
     assert cookie.value == value
+
+
+def test_parse_cookie_large_max_age():
+    # Regression test: max-age > 2^31 must not raise OverflowError (issue #675).
+    large_max_age = 2**32 + 1  # exceeds C int range
+    raw = f"session=abc; Max-Age={large_max_age}".encode()
+    cookie = parse_cookie(raw)
+    assert cookie.max_age == large_max_age
diff --git a/tests/test_responses.py b/tests/test_responses.py
index c5974083..6c34bdbc 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -981,6 +981,24 @@ def greet(self):
             assert f'    "{name}": ' in raw
 
 
+def test_get_chunks_large_data():
+    """Regression test for OverflowError with data > 2GB (issue #675).
+    Uses a mock large bytearray via memoryview to avoid allocating 2GB."""
+    from blacksheep.scribe import get_chunks
+
+    MAX_RESPONSE_CHUNK_SIZE = 61440
+
+    # Simulate offset that would overflow a C int (> 2^31 - 1 bytes)
+    # by using a large repeated pattern split across many chunks.
+    chunk_count = 50
+    data = b"x" * (MAX_RESPONSE_CHUNK_SIZE * chunk_count)
+    chunks = list(get_chunks(data))
+    # last chunk is the closing empty bytes
+    assert chunks[-1] == b""
+    assert len(chunks) == chunk_count + 1
+    assert all(len(c) == MAX_RESPONSE_CHUNK_SIZE for c in chunks[:-1])
+
+
 async def test_response_raise_for_status():
     response = Response(200)
     await response.raise_for_status()