CVE-2026-78663
Description
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.
Statement
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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.3 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | High |
| Availability Impact | Low | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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