CVE-2026-43678

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.

CVSS 3.1

5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

0.4% chance of exploitation in the next 30 days; higher than 31% of CVEs (scores of 2026-10-25)

CWEs

CWE-20, CWE-770

Published

2026-08-20

Modified

2026-10-18

Record from

the NVD, synced 2026-10-19

Affected

• apple:swiftnio

References

• https://github.com/apple/swift-nio/security/advisories/GHSA-qcc5-f287-vgmq

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