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)

Published · last modified .

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.

EPSS exploit prediction

EPSS: 0.004 (29.1th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-43678: held from 0.003 to 0.004.

EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001

Affected products

Weakness classification (CWE)

References

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.