CVE-2026-128132: Security vulnerability

Published Nov 13, 2026

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, the WebSocket reader continues parsing frames already received after the receive queue pauses the transport, and empty messages are not counted toward the queue size. With permessage-deflate, one read of compressed frames can add many megabytes of decompressed messages to the receive queue. A remote peer can send many small or compressed messages faster than the application consumes them and cause excessive memory use in a server or client. This issue is fixed in version 3.14.4.

Frequently Asked Questions

Who is exposed to this issue?

Both aiohttp servers and clients using WebSocket connections are exposed if they run a version prior to 3.14.4. Exposure is most relevant where a remote WebSocket peer can send messages faster than the application consumes them.

What does an attacker need to do to trigger excessive memory use?

A remote peer needs to send many small messages or compressed WebSocket frames faster than the receiving application drains its receive queue. With permessage-deflate enabled, compressed frames can expand into many megabytes of queued decompressed messages.

Is permessage-deflate required for exploitation?

No. The issue can be triggered by many small messages because empty messages are not counted toward queue size. permessage-deflate can make the memory impact substantially larger by allowing compressed input to produce large decompressed queued messages.

What should be done if an affected deployment cannot be upgraded immediately?

The provided information identifies version 3.14.4 as the fix but does not specify a workaround. Prioritize limiting or monitoring untrusted WebSocket peers and their message rates until the affected aiohttp component can be upgraded.

CVE-2026-128132: Security vulnerability

Frequently Asked Questions

Who is exposed to this issue?

What does an attacker need to do to trigger excessive memory use?

Is permessage-deflate required for exploitation?

What should be done if an affected deployment cannot be upgraded immediately?

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Frequently Asked Questions

Who is exposed to this issue?

What does an attacker need to do to trigger excessive memory use?

Is permessage-deflate required for exploitation?

What should be done if an affected deployment cannot be upgraded immediately?