CVE-2026-43678
Received Received - Intake

Unauthenticated DoS in SwiftNIO WebSocket Servers

Publication date: 2026-08-20

Last updated on: 2026-08-20

Assigner: Apple Inc.

Description
An unauthenticated remote peer can crash any NIOWebSocket-based server (including Vapor and Hummingbird) with a single 11-byte frame sent after a completed WebSocket handshake, dropping all active connections until the process restarts. This vulnerability is addressed in swift-nio version 2.101.0.

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Meta Information

Published
2026-08-20
Last Modified
2026-08-20
Generated
2026-08-20
AI Q&A
2026-08-20
EPSS Evaluated
N/A
NVD
CVE-2026-43678
EUVD
EUVD-2026-63577

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
apple container to 1.1.0 (exc)
apple container From 1.2.0 (inc)
apple swift_nio 2.101.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

Attack-Flow Graph

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Executive Summary

CVE-2026-43678 is a vulnerability where an unauthenticated remote peer can crash any NIOWebSocket-based server, including Vapor and Hummingbird, by sending a single 11-byte frame after a completed WebSocket handshake. This causes all active connections to drop until the server process restarts.

Impact Analysis

This vulnerability can disrupt service availability by crashing the server, leading to downtime for all connected clients. It requires no authentication, making it exploitable by any remote attacker with network access to the server.

Mitigation Strategies

Upgrade to swift-nio version 2.101.0 or later to address the vulnerability. Ensure no unauthenticated remote peers can send malicious 11-byte frames after WebSocket handshake completion.

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