VU#885548: Denial-of-service vulnerability in HTTP/2 servers via stalled flow-control conditions

Summary

Overview A denial-of-service (DoS) vulnerability exists in some HTTP/2 server implementations that fail to adequately limit resource consumption when buffering response data under stalled flow-control conditions. A remote, unauthenticated attacker can trigger memory exhaustion and service interruption by using standard flow-control parameters such as SETTINGS_INITIAL_WINDOW_SIZE = 0 to stall outbound data for multiple simultaneous request streams. Description HTTP/2 is a widely used application-layer protocol that supports multiplexing, header compression, and flow-control mechanisms to regulate the transmission of data between web browsers and servers. Flow control is designed to prevent senders from overwhelming receivers and relies on client-advertised window sizes to determine the maximum volume of unacknowledged data that can be in...

Why it matters

CERT/CC notes often cover coordinated disclosures, multi-vendor exposure, infrastructure risk, or cases where remediation guidance is still developing.

Operator check

Review the CERT/CC Vulnerability Note and compare the affected vendor and product list against your inventory. Apply vendor fixes or compensating controls for servers via stalled flow-control conditions where available.

Sources