Vulnerability in Cloudflare Quiche - Incorrect Congestion Window Growth

CVE-2025-4820

What is CVE-2025-4820?

The Cloudflare Quiche is susceptible to a vulnerability involving incorrect congestion window growth, allowing unauthenticated remote attackers to manipulate data transfer rates. By completing a handshake, the attacker can exploit the congestion control mechanisms through an opportunistic ACK attack, potentially allowing more data to be in transit than the underlying network can sustain. This could lead to degraded performance and unreliable connections for users.

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