diff --git a/CHANGES/10355.bugfix.rst b/CHANGES/10355.bugfix.rst
new file mode 100644
index 00000000000..99db3382cd4
--- /dev/null
+++ b/CHANGES/10355.bugfix.rst
@@ -0,0 +1,5 @@
+Fixed missing CRLF in a malformed chunked encoded message body -- by
+:user:`xdegaye`.
+
+A missing CRLF in a chunked encoded message now raises an exception instead of
+silently discarding the following part of the message.
diff --git a/aiohttp/http_parser.py b/aiohttp/http_parser.py
index d44f4cb12f1..ddb03a15ef7 100644
--- a/aiohttp/http_parser.py
+++ b/aiohttp/http_parser.py
@@ -880,6 +880,19 @@ def feed_data(
                         chunk = chunk[len(SEP) :]
                         self._chunk = ChunkState.PARSE_CHUNKED_SIZE
                     else:
+                        length = len(chunk)
+                        if (
+                            self._lax
+                            and length
+                            or (
+                                not self._lax
+                                and (length and chunk[:1] != SEP[:1] or length > 1)
+                            )
+                        ):
+                            exc = TransferEncodingError("Missing CRLF at chunk end")
+                            set_exception(self.payload, exc)
+                            raise exc
+                        # Get the CRLF or the missing LF in the next chunk.
                         self._chunk_tail = chunk
                         return False, b""
 
diff --git a/tests/test_http_parser.py b/tests/test_http_parser.py
index f7489bc7656..39308f9996b 100644
--- a/tests/test_http_parser.py
+++ b/tests/test_http_parser.py
@@ -1761,6 +1761,69 @@ async def test_parse_chunked_payload_split_end_trailers4(
         assert out.is_eof()
         assert b"asdf" == b"".join(out._buffer)
 
+    async def test_parse_chunked_payload_split_CRLF(
+        self, protocol: BaseProtocol
+    ) -> None:
+        loop = asyncio.get_running_loop()
+        for lax, SEP in ((False, b"\r\n"), (True, b"\n")):
+            out = aiohttp.StreamReader(protocol, 2**16, loop=loop)
+            p = HttpPayloadParser(out, chunked=True, lax=lax)
+            p.feed_data(b"4\r\nasdf", SEP=SEP)  # type: ignore[arg-type]
+            p.feed_data(b"\r\n0\r\n\r\n", SEP=SEP)  # type: ignore[arg-type]
+
+            assert out.is_eof()
+            assert b"asdf" == b"".join(out._buffer)
+
+    async def test_parse_chunked_payload_split_CRLF2(
+        self, protocol: BaseProtocol
+    ) -> None:
+        loop = asyncio.get_running_loop()
+        for lax, SEP in ((False, b"\r\n"), (True, b"\n")):
+            out = aiohttp.StreamReader(protocol, 2**16, loop=loop)
+            p = HttpPayloadParser(out, chunked=True, lax=lax)
+            p.feed_data(b"4\r\nasdf\r", SEP=SEP)  # type: ignore[arg-type]
+            p.feed_data(b"\n0\r\n\r\n", SEP=SEP)  # type: ignore[arg-type]
+
+            assert out.is_eof()
+            assert b"asdf" == b"".join(out._buffer)
+
+    async def test_parse_chunked_payload_split_CRLF3(
+        self, protocol: BaseProtocol
+    ) -> None:
+        loop = asyncio.get_running_loop()
+        for lax, SEP in ((False, b"\r\n"), (True, b"\n")):
+            out = aiohttp.StreamReader(protocol, 2**16, loop=loop)
+            p = HttpPayloadParser(out, chunked=True, lax=lax)
+            with pytest.raises(http_exceptions.TransferEncodingError):
+                p.feed_data(b"4\r\nasdf", SEP=SEP)  # type: ignore[arg-type]
+                p.feed_data(b"X\n0\r\n\r\n", SEP=SEP)  # type: ignore[arg-type]
+            exc = out.exception()
+            assert isinstance(exc, http_exceptions.TransferEncodingError)
+            assert "Missing CRLF" in exc.args[0]
+
+    async def test_parse_chunked_payload_split_CRLF4(
+        self, protocol: BaseProtocol
+    ) -> None:
+        out = aiohttp.StreamReader(protocol, 2**16, loop=asyncio.get_running_loop())
+        p = HttpPayloadParser(out, chunked=True)
+        with pytest.raises(http_exceptions.TransferEncodingError):
+            p.feed_data(b"4\r\nasdfX")
+            p.feed_data(b"\n0\r\n\r\n")
+        exc = out.exception()
+        assert isinstance(exc, http_exceptions.TransferEncodingError)
+        assert "Missing CRLF" in exc.args[0]
+
+    async def test_parse_chunked_payload_missing_CRLF(
+        self, protocol: BaseProtocol
+    ) -> None:
+        out = aiohttp.StreamReader(protocol, 2**16, loop=asyncio.get_running_loop())
+        p = HttpPayloadParser(out, chunked=True)
+        with pytest.raises(http_exceptions.TransferEncodingError):
+            p.feed_data(b"4\r\nasdf\rX0\r\n\r\n")
+        exc = out.exception()
+        assert isinstance(exc, http_exceptions.TransferEncodingError)
+        assert "Missing CRLF" in exc.args[0]
+
     async def test_http_payload_parser_length(self, protocol: BaseProtocol) -> None:
         out = aiohttp.StreamReader(protocol, 2**16, loop=asyncio.get_running_loop())
         p = HttpPayloadParser(out, length=2)