Bug 2571771 (CVE-2026-119234)

Summary: CVE-2026-119234 mvfst: mvfst: Denial of Service via fragmented stream data
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in mvfst. This vulnerability allows a remote, unauthenticated attacker to cause a Denial of Service (DoS) by sending numerous small, non-contiguous stream fragments. Because out-of-order data is not properly merged or compacted, processing these fragments causes the endpoint to exhaust memory and CPU resources, resulting in service disruption.
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Description OSIDB Bzimport 2026-11-11 17:01:23 UTC 
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.