CVE-2026-119234 · Package
NO FIX YET · SEE WHAT TO DO
mvfst, Meta's QUIC transport library, does not merge or compact out-of-order STREAM frame data well, so a small fragment can keep a much larger receive buffer alive. A remote, unauthenticated peer can send many small non-contiguous fragments to make an endpoint use memory beyond its advertised receive window and spend growing CPU time, causing denial of service.
first public Nov 11, 2026 · 1 source
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Applications that embed mvfst as their QUIC transport and accept connections from untrusted peers are exposed, since the flaw is triggered by remote QUIC traffic without authentication. Services that do not use mvfst, or that only talk to trusted peers, can skip it. The sources do not say which downstream products bundle mvfst.
Not affected if does-not-use-mvfst, trusted-peers-only
Who cares c++, mvfst, quic
mvfst.v2026.11.09.0.v2026.11.09.0 are affected; move to v2026.11.09.0 or later.mvfst did not adequately merge or compact out-of-order STREAM frame data, and a small received fragment could keep a much larger receive buffer alive. QUIC flow control limits the number of buffered stream bytes, but not this per-fragment memory and bookkeeping. A remote, unauthenticated QUIC peer could send many small, non-contiguous stream fragments to make an endpoint consume memory far in excess of its advertised receive window and spend increasing CPU time reassembling stream data, leading to denial of service. This issue affects mvfst versions prior to v2026.11.09.0.
NVD data is provided by NIST and is public domain. Posts quoted belong to their authors.
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