CVE-2026-128126

AIOHTTP: Too many URL-encoded form fields block the event loop

Published Nov 13, 2026 CVSS 4.0 · 8.7 High EPSS n/a KEV · Not listed
Description
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, Request.post() does not limit the number of fields in a URL-encoded form body, and inserting many repeated keys into MultiDict takes quadratic time on the event loop. A remote attacker can send a form POST within client_max_size to a handler that calls Request.post() and block the event loop. This issue is fixed in version 3.14.4.

Analysis

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Remediation

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Tracking

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Advisories

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History
Type Values Removed Values Added
Description AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, Request.post() does not limit the number of fields in a URL-encoded form body, and inserting many repeated keys into MultiDict takes quadratic time on the event loop. A remote attacker can send a form POST within client_max_size to a handler that calls Request.post() and block the event loop. This issue is fixed in version 3.14.4.
Title AIOHTTP: Too many URL-encoded form fields block the event loop
Weaknesses CWE-407
References
Metrics cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N'}

Subscriptions

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Weaknesses
  • CWE-407

    Inefficient Algorithmic Complexity

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 13, 2026, 8:27 PM
Reserved
Nov 12, 2026, 10:42 PM
Status
Received
Published
Nov 13, 2026, 9:17 PM
Modified
Nov 13, 2026, 9:17 PM