CVE-2026-43678: An unauthenticated remote peer can crash any NIOWebSocket-based server (including Vapor and Hummingbird) with

Q: How do I fix CVE-2026-43678?

swiftnio: upgrade to 2.101.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-43678 being exploited?

CVE-2026-43678 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-43678 affect?

CVE-2026-43678 affects swiftnio. Severity is medium (CVSS 5.3). 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. Thi

Q: How urgent is CVE-2026-43678?

Priority 31/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-43678 is a medium-severity flaw (CVSS 5.3) affecting swiftnio. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-20, CWE-770
Published	2026-08-20
Last modified	2026-10-18

Publisher (CNA): Apple Inc. · Vendor: apple

Last updated 2026-10-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-08-20 19:16 UTCPublished CVE record published
2026-10-18 20:10 UTCUpdated Record last modified

apple swiftnio UPGRADE

Affected: < 2.101.0

Fixed in: 2.101.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy swiftnio || rpm -q swiftnio || swiftnio --version

2. UPGRADE to 2.101.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade swiftnio

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade swiftnio

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-43678?

swiftnio: upgrade to 2.101.0. Exact commands for each OS are on this page.

Is CVE-2026-43678 being exploited?

CVE-2026-43678 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-43678 affect?

CVE-2026-43678 affects swiftnio. Severity is medium (CVSS 5.3). 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. Thi

How urgent is CVE-2026-43678?

Priority 31/100. Remotely exploitable, no login, no user action

Software pages

Swift vulnerabilities

References

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