CVE-2025-69229
📋 TL;DR
AIOHTTP versions 3.13.2 and below contain a vulnerability where handling chunked HTTP messages can cause excessive blocking CPU usage. Attackers can exploit this by sending requests with many chunks, potentially causing denial of service as servers become unresponsive. This affects any Python application using AIOHTTP with request.read() endpoints.
💻 Affected Systems
- aiohttp
📦 What is this software?
Aiohttp by Aiohttp
⚠️ Risk & Real-World Impact
Worst Case
Complete server unavailability due to CPU exhaustion, leading to sustained denial of service affecting all users.
Likely Case
Temporary performance degradation where servers become slow or unresponsive for moderate periods (seconds to minutes) during attack bursts.
If Mitigated
Minimal impact with proper rate limiting and monitoring; brief performance spikes that don't affect overall availability.
🎯 Exploit Status
Exploitation requires sending HTTP requests with many small chunks, which is trivial to implement. No authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.13.3
Vendor Advisory: https://github.com/aio-libs/aiohttp/security/advisories/GHSA-g84x-mcqj-x9qq
Restart Required: Yes
Instructions:
1. Update aiohttp: pip install --upgrade aiohttp==3.13.3
2. Restart all affected Python applications
3. Verify the new version is active
🔧 Temporary Workarounds
Rate limiting chunked requests
allImplement request rate limiting or size limits for chunked transfer encoding
# Configure web server (nginx example)
# limit_req_zone $binary_remote_addr zone=chunklimit:10m rate=10r/s;
# limit_req zone=chunklimit burst=20;
Avoid request.read() in endpoints
allModify code to use alternative methods like request.text() or request.json() where possible
# Replace: await request.read()
# With: await request.text() # for text data
# Or: await request.json() # for JSON data
🧯 If You Can't Patch
- Implement strict rate limiting on HTTP endpoints using request.read()
- Deploy WAF rules to detect and block excessive chunked transfer encoding
🔍 How to Verify
Check if Vulnerable:
Check if aiohttp version <= 3.13.2 is installed and if any endpoints use request.read()Check Version:
python -c "import aiohttp; print(aiohttp.__version__)"Verify Fix Applied:
Confirm aiohttp version >= 3.13.3 and test chunked request handling📡 Detection & Monitoring
Log Indicators:
- High CPU usage spikes
- Slow response times for endpoints using request.read()
- Multiple chunked transfer encoding requests from single IPs
Network Indicators:
- HTTP requests with many Transfer-Encoding: chunked headers
- Unusually large number of small HTTP chunks
SIEM Query:
source="web_logs" Transfer-Encoding="chunked" | stats count by src_ip | where count > threshold