What is CVE-2026-43678?

CVE-2026-43678 is a medium-severity vulnerability in Apple Swift-Nio, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2026-08-20.

How severe is CVE-2026-43678?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Resource exhaustion in Apple Swift-Nio

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

Affected products

Apple Swift-nio

Weakness classification (CWE)

CWE-20 — Improper Input Validation
CWE-770 — Allocation of Resources Without Limits or Throttling

References

product-security@apple.com

Frequently asked questions

What is CVE-2026-43678?: CVE-2026-43678 is a medium-severity vulnerability in Apple Swift-Nio, classified under Improper Input Validation. CVSS score: 5.3/10. Published 2026-08-20.
How severe is CVE-2026-43678?: Medium severity. CVSS v3 base score is 5.3 out of 10.