HTTP response splitting in aiohttp - CVE-2026-50269
Published: June 9, 2026
Vulnerability identifier: #VU133988
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-50269
CWE-ID: CWE-113
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: aio-libs
Affected software:
aiohttp
aiohttp
Detailed vulnerability description
The vulnerability allows a remote attacker to inject additional headers or modify the contents of a request.
The vulnerability exists due to improper neutralization of crlf sequences in multipart headers when processing user-controlled header values. A remote attacker can supply crafted input to inject additional headers or modify the contents of a request.
The issue occurs if an application passes user-controlled strings into MultipartWriter.append(headers=...) or Payload.headers.
How to mitigate CVE-2026-50269
Install security update from vendor's website.