CVE-2026-78663

A flaw was found in Go's HTTP/2 server implementation. A remote attacker can bypass connection-level flow control limits—mechanisms that regulate incoming network data—potentially causing excessive memory consumption and a Denial of Service (DoS). This issue occurs because the server improperly refunds flow control credits twice for the same data: once when a client resets a stream, and again when the application reads the buffered data. Consequently, a malicious client can exceed configured connection buffer limits.

Red Hat has evaluated this vulnerability as having a Moderate security impact because, while remote unauthenticated clients can bypass configured connection receive buffer thresholds on affected HTTP/2 servers, overall resource exhaustion remains bounded. Exploitation is constrained by stream-level flow controls and limits on concurrent streams, which prevents an attacker from causing unbounded memory consumption or a complete denial of service. Go-based network services handling untrusted HTTP/2 traffic may experience elevated memory usage under sustained reset attacks, but typical deployments remain operational without catastrophic service disruption.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.