CVE-2026-43678 Denial of service in swift-nio
An unauthenticated remote attacker can crash NIOWebSocket-based servers by sending a specific 11-byte frame, requiring developers to upgrade swift-nio.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-43678?
CVE-2026-43678 is a medium-severity denial of service vulnerability in Apple swift-nio, published on 20 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Which versions are affected by CVE-2026-43678?
It affects 1 product.
Products include Apple Swiftnio.
How do I fix CVE-2026-43678?
No fix has been published for CVE-2026-43678 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-43678 being exploited?
There is no known exploitation of CVE-2026-43678 in the wild and no public exploit code.
Other vulnerabilities in Apple swift-nio
Sources
Also known as GHSA-qcc5-f287-vgmq.