CVE-2026-34516: AIOHTTP: Multipart Header Size Bypass
Summary
A response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability.
Impact
Multipart headers were not subject to the same size restrictions in place for normal headers, potentially allowing substantially more data to be loaded into memory than intended. However, other restrictions in place limit the impact of this vulnerability.
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Patch: https://github.com/aio-libs/aiohttp/commit/8a74257b3804c9aac0bf644af93070f68f6c5a6f
Other sources
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, a response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability. This issue has been patched in version 3.13.4.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/aiohttpto a version that resolves this vulnerability.Fixed in 3.13.4 - Upgrade
Upgrade
debian/python-aiohttpto a version that resolves this vulnerability.Fixed in 3.7.4-1+deb11u2Fixed in 3.14.1-4 - Upgrade
Upgrade
aiohttpto a version that resolves this vulnerability.Fixed in 3.13.4Patch 8a74257b3804c9aac0bf644af93070f68f6c5a6f