CVE-2026-61666 websocket-driver: Denial of service via malformed Host header
A remote attacker can crash a WebSocket server by sending a malformed Host header, causing an unhandled exception in the websocket-driver library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-61666?
CVE-2026-61666 is a high-severity denial of service vulnerability in faye websocket-driver-ruby, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
websocket-driver is a WebSocket protocol handler with pluggable I/O. Prior to 0.8.2, WebSocket::Driver.server() passes a malformed Host header to URI.parse in lib/websocket/http/request.rb without catching URI::InvalidURIError, allowing a remote client to crash a TCP-backed WebSocket server when the application does not catch the error from parse(). This issue is fixed in version 0.8.2.
Weakness: CWE-248
Which versions are affected by CVE-2026-61666?
2 open source packages ship an affected version, including websocket-driver.
| Package | Affected | Fixed in |
|---|---|---|
websocket-driver RubyGems | All versions | 0.8.2 |
websocket-driver RubyGems | All versions | 0.8.2 |
How do I fix CVE-2026-61666?
Upgrade websocket-driver to 0.8.2 or later.
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-2026-61666 being exploited?
There is no known exploitation of CVE-2026-61666 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-61666, GHSA-2x63-gw47-w4mm, MINI-2rpx-65c3-8mvf, MINI-85wv-pwpj-jxwr, UBUNTU-CVE-2026-61666.