CVE-2025-69227
Unknown Unknown - Not Provided
Denial of Service via POST Body in AIOHTTP

Publication date: 2026-01-06

Last updated on: 2026-01-06

Assigner: GitHub, Inc.

Description
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Versions 3.13.2 and below allow for an infinite loop to occur when assert statements are bypassed, resulting in a DoS attack when processing a POST body. If optimizations are enabled (-O or PYTHONOPTIMIZE=1), and the application includes a handler that uses the Request.post() method, then an attacker may be able to execute a DoS attack with a specially crafted message. This issue is fixed in version 3.13.3.
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Meta Information
Published
2026-01-06
Last Modified
2026-01-06
Generated
2026-06-16
AI Q&A
2026-01-06
EPSS Evaluated
2026-06-14
NVD
CVE-2025-69227
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
aio-libs aiohttp to 3.13.2 (inc)
aio-libs aiohttp 3.13.3
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-835 The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.
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Executive Summary

CVE-2025-69227 is a denial-of-service (DoS) vulnerability in the aiohttp Python package versions 3.13.2 and below. When Python optimizations are enabled (using the -O flag or PYTHONOPTIMIZE=1), assert statements are bypassed. If an application uses a handler that calls the Request.post() method to process POST request bodies, an attacker can send a specially crafted POST message that triggers an infinite loop during processing. This infinite loop causes the application to become unresponsive, resulting in a DoS condition. The issue was fixed in version 3.13.3 by replacing assert statements with explicit exception handling to properly detect and handle malformed multipart data. [1, 2]

Impact Analysis

This vulnerability can cause your aiohttp-based application to become unresponsive due to an infinite loop triggered by a maliciously crafted POST request when Python optimizations are enabled. This results in a denial-of-service (DoS) attack, potentially disrupting service availability and impacting users who rely on the application. [1]

Detection Guidance

Detection involves monitoring for application unresponsiveness or infinite loops when processing POST requests in aiohttp applications running with Python optimizations enabled (-O or PYTHONOPTIMIZE=1). Since the vulnerability triggers an infinite loop on specially crafted POST bodies processed by handlers using Request.post(), you can detect it by sending crafted POST requests to test endpoints and observing if the application hangs or consumes excessive CPU. Specific commands are not provided in the resources. [1]

Mitigation Strategies

The immediate mitigation is to upgrade aiohttp to version 3.13.3 or later, where the vulnerability is fixed by replacing assert statements with explicit exception handling to prevent infinite loops. Additionally, avoid running Python with optimizations enabled (-O or PYTHONOPTIMIZE=1) until the upgrade is applied, as the vulnerability only manifests under these conditions. [1, 2]

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