Cloudanix VulnDB

CVE-2026-78663

Critical · 9.1

CVSS

9.1

EPSS

0.6%

Published

Oct 8, 2026

CISA due date

—

The record

The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.

Affected packages

Ecosystem Package Introduced Fixed

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