Package Instance

aiohttp vulnerable to Denial of Service when trying to parse malformed POST requests
### Summary
An attacker can send a specially crafted POST (multipart/form-data) request. When the aiohttp server processes it, the server will enter an infinite loop and be unable to process any further requests.

### Impact
An attacker can stop the application from serving requests after sending a single request.

-------

For anyone needing to patch older versions of aiohttp, the minimum diff needed to resolve the issue is (located in `_read_chunk_from_length()`):

```diff
diff --git a/aiohttp/multipart.py b/aiohttp/multipart.py
index 227be605c..71fc2654a 100644
--- a/aiohttp/multipart.py
+++ b/aiohttp/multipart.py
@@ -338,6 +338,8 @@ class BodyPartReader:
         assert self._length is not None, "Content-Length required for chunked read"
         chunk_size = min(size, self._length - self._read_bytes)
         chunk = await self._content.read(chunk_size)
+        if self._content.at_eof():
+            self._at_eof = True
         return chunk
 
     async def _read_chunk_from_stream(self, size: int) -> bytes:
```

This does however introduce some very minor issues with handling form data. So, if possible, it would be recommended to also backport the changes in:
https://github.com/aio-libs/aiohttp/commit/cebe526b9c34dc3a3da9140409db63014bc4cf19
https://github.com/aio-libs/aiohttp/commit/7eecdff163ccf029fbb1ddc9de4169d4aaeb6597
https://github.com/aio-libs/aiohttp/commit/f21c6f2ca512a026ce7f0f6c6311f62d6a638866

AIOHTTP vulnerable to  denial of service through large payloads
### Summary
A request can be crafted in such a way that an aiohttp server's memory fills up uncontrollably during processing.

### Impact
If an application includes a handler that uses the `Request.post()` method, an attacker may be able to freeze the server by exhausting the memory.

-----

Patch: https://github.com/aio-libs/aiohttp/commit/b7dbd35375aedbcd712cbae8ad513d56d11cce60

AIOHTTP has unicode match groups in regexes for ASCII protocol elements
### Summary

The parser allows non-ASCII decimals to be present in the Range header.

### Impact

There is no known impact, but there is the possibility that there's a method to exploit a request smuggling vulnerability.

----

Patch: https://github.com/aio-libs/aiohttp/commit/c7b7a044f88c71cefda95ec75cdcfaa4792b3b96

AIOHTTP is vulnerable to HTTP Request/Response Smuggling through incorrect parsing of chunked trailer sections
### Summary
The Python parser is vulnerable to a request smuggling vulnerability due to not parsing trailer sections of an HTTP request.

### Impact
If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections.

----

Patch: https://github.com/aio-libs/aiohttp/commit/e8d774f635dc6d1cd3174d0e38891da5de0e2b6a

AIOHTTP vulnerable to DoS through chunked messages
### Summary

Handling of chunked messages can result in excessive blocking CPU usage when receiving a large number of chunks.

### Impact

If an application makes use of the `request.read()` method in an endpoint, it may be possible for an attacker to cause the server to spend a moderate amount of blocking CPU time (e.g. 1 second) while processing the request. This could potentially lead to DoS as the server would be unable to handle other requests during that time.

-----

Patch: https://github.com/aio-libs/aiohttp/commit/dc3170b56904bdf814228fae70a5501a42a6c712
Patch: https://github.com/aio-libs/aiohttp/commit/4ed97a4e46eaf61bd0f05063245f613469700229