PROXYGEN · CVE-2026-119233 · Runtime
NO FIX YET · SEE WHAT TO DO
Proxygen's HTTP/3 codec buffers incomplete non-DATA frames without a length limit and rescans them on each new fragment. A remote, unauthenticated HTTP/3 client can declare a huge frame and send it slowly, causing unbounded memory growth and quadratic CPU use that leads to denial of service.
first public Nov 11, 2026 · 1 source
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Servers and services built on proxygen that accept HTTP/3 connections from the internet are exposed, since the attack needs no account. Services that do not use proxygen, or do not accept HTTP/3, can skip it. The sources do not say whether any configuration disables the affected path.
Not affected if no-http3, not-proxygen
Who cares c++, http3, proxygen, self-hosted
v2026.11.09.00.v2026.11.09.00 or later.proxygen's HTTP/3 codec buffered an incomplete non-DATA frame, such as a control-stream frame, a frame of an unknown or reserved type, or a HEADERS frame, until its entire declared length had arrived, without limiting that length, and re-scanned all buffered data each time more bytes arrived. A remote, unauthenticated HTTP/3 peer could declare a very large frame and deliver it slowly, causing unbounded memory growth and CPU usage that grows quadratically with the number of fragments, leading to denial of service. This issue affects proxygen versions prior to v2026.11.09.00.
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