AIKIDO-2026-241554
h2 is vulnerable to Denial of Service (DoS)
25
Low Risk
This Affects:
h2TL;DR
The h2 HTTP/2 stack accepts and queues empty DATA frames without a cap. HTTP/2 flow control bounds payload bytes, not the number of frames, so a peer can fragment traffic into many empty frames and force unbounded queue growth, or a panic if the length overflows, when streams are not drained. The fix adds a connection-level budget for DATA framing overhead, discards non-final empty DATA frames after flow-control accounting, and closes the connection with ENHANCE_YOUR_CALM when that budget is exhausted.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and your application uses HTTP/2 via h2 (as a server or client) without fully draining incoming request or response bodies, for example a proxy applying backpressure or a client that delays reading the body.
Background info
h2 is vulnerable to Denial of Service (DoS) in versions 0.1.0 - 0.4.15.
How to fix this
Upgrade the h2 library to the patch version.
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