HTTP Response Splitting Affecting aiohttp package, versions [,3.13.4)
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- published2 Apr 2026
- disclosed1 Apr 2026
- creditvmfunc, oxqnd
Introduced: 1 Apr 2026
NewCVE-2026-34520 (opens in a new tab)Common Vulnerabilities and Exposures (CVE) are common identifiers for publicly known security vulnerabilities
Common Weakness Enumeration (CWE) is a category system for software weaknesses
How to fix?
Upgrade aiohttp to version 3.13.4 or higher.
Overview
Affected versions of this package are vulnerable to HTTP Response Splitting in the llhttp component. An attacker can manipulate HTTP response headers by injecting null bytes or control characters, causing headers to be interpreted differently by various components, which may lead to security bypass or inconsistent behavior between the application and reverse proxies.