How the CVE Works
The vulnerability exists in Django’s `strip_tags()` function, which fails to efficiently handle malformed HTML input containing excessive nested or unclosed tags. When processing such input, the function enters an inefficient parsing loop, causing high CPU usage and significantly slowing down request processing. This allows attackers to craft malicious payloads with thousands of incomplete tags (e.g., <div<div<div<) that trigger excessive resource consumption, leading to denial-of-service conditions. The issue affects Django’s template system when using the `striptags` filter, as it relies on the vulnerable `strip_tags()` utility.
DailyCVE Form:
Platform: Django
Version: 4.2-4.2.20, 5.1-5.1.8, 5.2-5.2.0
Vulnerability: DoS via `strip_tags()`
Severity: Moderate
Date: May 8, 2025
What Undercode Say:
Exploitation:
1. Payload Example:
<div<div<div<div<div<div<div<div<div<div<div<div<div<div<div...
2. Proof of Concept:
import requests
payload = "
<
div" 100000 Crafted payload
response = requests.post("https://vulnerable-site.com/form", data={"input": payload})
3. Impact: CPU exhaustion, degraded server performance.
Mitigation:
1. Upgrade Django:
pip install --upgrade django==4.2.21
2. Input Validation:
from django.core.exceptions import ValidationError
def validate_html_length(value):
if len(value) > 1000: Limit input size
raise ValidationError("Input too large.")
3. Rate Limiting: Use Django middleware to restrict repeated requests.
Detection:
- Log Analysis: Monitor logs for unusually large HTML inputs.
grep -E "strip_tags|striptags" /var/log/django/error.log
- Performance Metrics: Track CPU spikes during template rendering.
Patch Analysis:
The fix optimizes the HTML tag parsing logic in `strip_tags()` to exit early on malformed structures.
References:
- Django Security Releases: [bash]
- CVE Details: [NVD Link]
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
