CVE-2026-73228

Summary

While investigating Django REST Framework's request parsing behavior, I identified that DRF's high-level request.data parsing appears to bypass Django's configured DATA_UPLOAD_MAX_MEMORY_SIZE protection for application/json and application/x-www-form-urlencoded request bodies.

In the tested configurations, Django correctly raises RequestDataTooBig when applications access request.body or Django's native request.POST, but DRF successfully parses the same oversized payloads through request.data.

This behavior appears to occur because DRF passes the underlying HttpRequest object directly to parsers, which consume the request stream through Django's lower-level streaming interface rather than the guarded request.body path.

I am reporting this privately because I am unsure whether this behavior is considered part of DRF's intended security boundary, but it appears to bypass a documented Django request-size protection for common DRF request parsing paths and may have availability implications.

What I Verified

I verified the behavior locally using the following combinations:

• Django 6.0.7 + DRF 3.17.1 → Affected
• Django 6.0.7 + DRF current upstream main → Affected

For both versions, the observed behavior was:

Django request.body
→ RequestDataTooBig

Django request.POST (application/x-www-form-urlencoded)
→ RequestDataTooBig

Django request.read()
→ Reads the entire oversized request body

DRF request.data
→ Successfully parses oversized JSON and urlencoded request bodies

I also confirmed that:

• multipart/form-data remains protected because DRF delegates multipart parsing to Django's multipart parser.
• The behavior reproduces on both direct WSGI and ASGI servers without a reverse proxy or external request-size middleware.

Technical Details

The relevant execution flow is:

APIView

↓

rest_framework.request.Request

↓

request.data

↓

Request._load_data_and_files()

↓

Request._parse()

↓

Request._load_stream()

↓

self._stream = self._request

↓

JSONParser.parse(...)
or
FormParser.parse(...)

↓

stream.read() / json.load(...)

The important implementation detail is that DRF assigns the original Django HttpRequest object as the parser stream.

Unlike request.body and Django's native form parsing, consuming the stream through HttpRequest.read() does not trigger Django's RequestDataTooBig protection.

As a result, DRF's built-in parsers successfully consume oversized request bodies that Django itself would reject through its higher-level request interfaces.

Reproduction Steps

Environment

Python 3.13

Django 6.0.7

Django REST Framework 3.17.1 (also reproduced on current upstream main)

Configure:

DATA_UPLOAD_MAX_MEMORY_SIZE = 10

Create a simple DRF API view:

from rest_framework.views import APIView
from rest_framework.response import Response

class DemoView(APIView):
    def post(self, request):
        return Response(request.data)

Start the application.

Send an oversized JSON request:

POST /demo
Content-Type: application/json
Content-Length: >10 bytes

Example:

{
  "value": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA..."
}

Observed:

HTTP 200

JSON successfully parsed

Now compare against:

request.body

Observed:

RequestDataTooBig

Likewise, compare against:

request.POST

using

application/x-www-form-urlencoded

Observed:

RequestDataTooBig

This demonstrates different enforcement depending on which request API is used.

Root Cause

Django documents HttpRequest.read() as a streaming interface.

DRF exposes request.data as the primary high-level request parsing API.

Currently, DRF forwards the raw Django request stream directly to parsers before any request-size validation equivalent to Django's request.body path occurs.

Consequently:

• JSONParser
• FormParser

fully…

Summary

While investigating Django REST Framework's request parsing behavior, I identified that DRF's high-level request.data parsing appears to bypass Django's configured DATA_UPLOAD_MAX_MEMORY_SIZE protection for application/json and application/x-www-form-urlencoded request bodies.

In the tested configurations, Django correctly raises RequestDataTooBig when applications access request.body or Django's native request.POST, but DRF successfully parses the same oversized payloads through request.data.

This behavior appears to occur because DRF passes the underlying HttpRequest object directly to parsers, which consume the request stream through Django's lower-level streaming interface rather than the guarded request.body path.

I am reporting this privately because I am unsure whether this behavior is considered part of DRF's intended security boundary, but it appears to bypass a documented Django request-size protection for common DRF request parsing paths and may have availability implications.

What I Verified

I verified the behavior locally using the following combinations:

• Django 6.0.7 + DRF 3.17.1 → Affected
• Django 6.0.7 + DRF current upstream main → Affected

For both versions, the observed behavior was:

Django request.body
→ RequestDataTooBig

Django request.POST (application/x-www-form-urlencoded)
→ RequestDataTooBig

Django request.read()
→ Reads the entire oversized request body

DRF request.data
→ Successfully parses oversized JSON and urlencoded request bodies

I also confirmed that:

• multipart/form-data remains protected because DRF delegates multipart parsing to Django's multipart parser.
• The behavior reproduces on both direct WSGI and ASGI servers without a reverse proxy or external request-size middleware.

Technical Details

The relevant execution flow is:

APIView

↓

rest_framework.request.Request

↓

request.data

↓

Request._load_data_and_files()

↓

Request._parse()

↓

Request._load_stream()

↓

self._stream = self._request

↓

JSONParser.parse(...)
or
FormParser.parse(...)

↓

stream.read() / json.load(...)

The important implementation detail is that DRF assigns the original Django HttpRequest object as the parser stream.

Unlike request.body and Django's native form parsing, consuming the stream through HttpRequest.read() does not trigger Django's RequestDataTooBig protection.

As a result, DRF's built-in parsers successfully consume oversized request bodies that Django itself would reject through its higher-level request interfaces.

Reproduction Steps

Environment

Python 3.13

Django 6.0.7

Django REST Framework 3.17.1 (also reproduced on current upstream main)

Configure:

DATA_UPLOAD_MAX_MEMORY_SIZE = 10

Create a simple DRF API view:

from rest_framework.views import APIView
from rest_framework.response import Response

class DemoView(APIView):
    def post(self, request):
        return Response(request.data)

Start the application.

Send an oversized JSON request:

POST /demo
Content-Type: application/json
Content-Length: >10 bytes

Example:

{
  "value": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA..."
}

Observed:

HTTP 200

JSON successfully parsed

Now compare against:

request.body

Observed:

RequestDataTooBig

Likewise, compare against:

request.POST

using

application/x-www-form-urlencoded

Observed:

RequestDataTooBig

This demonstrates different enforcement depending on which request API is used.

Root Cause

Django documents HttpRequest.read() as a streaming interface.

DRF exposes request.data as the primary high-level request parsing API.

Currently, DRF forwards the raw Django request stream directly to parsers before any request-size validation equivalent to Django's request.body path occurs.

Consequently:

• JSONParser
• FormParser

fully…

Django REST framework is a toolkit for building Web APIs. Prior to 3.17.2, Django REST Framework's request.data parsing in rest_framework/request.py Request._parse() passes the underlying HttpRequest stream to JSONParser and FormParser for application/json and application/x-www-form-urlencoded bodies, bypassing Django's DATA_UPLOAD_MAX_MEMORY_SIZE protection and allowing oversized request bodies to consume additional memory and CPU. This issue is fixed in version 3.17.2.

These are all security issues fixed in the python313-djangorestframework-3.18.0-2.1 package on the GA media of openSUSE Tumbleweed.