CVE-2025-69230: AIOHTTP Logging Storm Vulnerability

CVE-2025-69230 Overview

CVE-2025-69230 is a resource exhaustion vulnerability in AIOHTTP, an asynchronous HTTP client/server framework for asyncio and Python. In versions 3.13.2 and below, reading multiple invalid cookies can lead to a logging storm. If the cookies attribute is accessed in an application, an attacker may be able to trigger a storm of warning-level logs using a specially crafted Cookie header. This issue has been classified as CWE-779 (Logging of Excessive Data) and is fixed in version 3.13.3.

Critical Impact

Attackers can cause excessive logging activity by sending specially crafted Cookie headers to AIOHTTP-based applications, potentially leading to log file exhaustion, disk space depletion, and degraded application performance.

Affected Products

• AIOHTTP versions 3.13.2 and below
• Python applications using AIOHTTP's cookie parsing functionality
• Web servers and applications that access the cookies attribute

Discovery Timeline

• 2026-01-06 - CVE-2025-69230 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-69230

Vulnerability Analysis

This vulnerability stems from improper logging behavior when processing malformed cookie headers in AIOHTTP. When an application accesses the cookies attribute on an incoming request, the framework parses the Cookie header. Prior to the fix, each invalid cookie encountered would generate a separate warning-level log entry. An attacker can exploit this behavior by crafting a Cookie header containing numerous invalid cookie entries, causing the application to generate an excessive volume of log messages.

The vulnerability represents a denial-of-service vector through log exhaustion. While the direct impact on confidentiality and integrity is limited, the operational impact can be significant as log files grow rapidly, potentially filling disk space, overwhelming log aggregation systems, or obscuring legitimate security events in a flood of cookie-related warnings.

Root Cause

The root cause lies in CWE-779 (Logging of Excessive Data). The AIOHTTP cookie parsing implementation logged a warning for every individual invalid cookie encountered in a request header. This per-cookie logging approach did not account for the possibility of attackers sending numerous malformed cookies in a single request, creating an amplification effect where one HTTP request could generate many log entries.

Attack Vector

The attack can be executed remotely over the network without authentication. An attacker sends HTTP requests containing Cookie headers with multiple invalid cookie entries to any AIOHTTP-based application that accesses the cookies attribute. Each malformed cookie triggers a warning log, allowing a single request to generate disproportionate logging activity. This is particularly effective against applications that process high volumes of requests or have limited log storage capacity.

     i = 0
     n = len(header)
 
+    invalid_names = []
     while i < n:
         # Use the same pattern as parse_set_cookie_headers to find cookies
         match = _COOKIE_PATTERN.match(header, i)

Source: GitHub Commit Update

The patch introduces an invalid_names list to aggregate invalid cookie names, allowing the framework to consolidate logging rather than emitting a separate warning for each invalid cookie. This reduces the amplification potential of the attack.

Detection Methods for CVE-2025-69230

Indicators of Compromise

• Unusual spikes in warning-level log volume related to cookie parsing
• HTTP requests containing abnormally long or numerous Cookie header entries
• Rapid disk space consumption in log directories
• Log aggregation system alerts for excessive warning messages from AIOHTTP applications

Detection Strategies

• Monitor log file growth rates for anomalous patterns indicating potential logging storm attacks
• Implement rate limiting on incoming requests with unusually large Cookie headers
• Configure log analysis tools to detect repetitive cookie-related warning patterns
• Review web server access logs for requests with suspiciously large Cookie header sizes

Monitoring Recommendations

• Set up alerts for rapid log volume increases in AIOHTTP application logs
• Monitor disk I/O and storage utilization on systems running AIOHTTP-based applications
• Implement log rotation with appropriate size limits to prevent disk exhaustion
• Track Cookie header sizes in web application firewall (WAF) or reverse proxy logs

How to Mitigate CVE-2025-69230

Immediate Actions Required

• Upgrade AIOHTTP to version 3.13.3 or later immediately
• Review application logs for signs of exploitation attempts
• Implement log rotation and size limits if not already configured
• Consider rate limiting requests with abnormal Cookie header patterns

Patch Information

The vulnerability is fixed in AIOHTTP version 3.13.3. The fix modifies the cookie parsing logic in aiohttp/_cookie_helpers.py to aggregate invalid cookie names and log them once per header rather than individually. This change was implemented in commit 64629a0834f94e46d9881f4e99c41a137e1f3326. For detailed information, see the GitHub Security Advisory GHSA-fh55-r93g-j68g.

Workarounds

• Implement request filtering at the reverse proxy or WAF level to reject requests with excessively large or numerous cookies
• Configure log rotation policies with aggressive size limits to mitigate disk exhaustion risk
• Deploy log sampling or rate limiting for cookie-related warning messages
• Consider implementing custom cookie parsing with controlled logging behavior until upgrade is possible

# Configuration example - Log rotation for AIOHTTP applications
# Add to /etc/logrotate.d/aiohttp
/var/log/aiohttp/*.log {
    daily
    rotate 7
    compress
    delaycompress
    missingok
    notifempty
    maxsize 100M
    create 0640 www-data www-data
}