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High, CVSS 8.9amended

websocket-driver-ruby: Denial of service via malformed Host header

CVE-2026-61666GHSA-2x63-gw47-w4mm

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (websocket-driver 0.8.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
8.9 · 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 · score source
EPSS
  • CVE-2026-61666: 0.45% estimated exploitation activity in the next 30 days; percentile 38.73 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact If this library is used to implement a WebSocket server on top of a TCP server, by using the `WebSocket::Driver.server()` method, then a client can cause the server to crash by sending a `Host` header that is not a valid `host[:port]` string. When this happens, a `URI::InvalidURIError` exception is raised which is not caught, and this can cause the server process to crash if the application does not catch the error from the `parse()` method itself.

Patches The issue has been patched in version 0.8.2 by making the request parser catch `URI::InvalidURIError` and enter an error state if the `Host` header is malformed. This means the request is considered invalid and should not establish a WebSocket connection.

Workarounds No known workarounds exist.

Acknowledgements This issue was discovered and reported by Pranjali Thakur, DepthFirst Security Research Team.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from osv record GHSA-2x63-gw47-w4mm

  2. Revision 2 · amended ·

    Amended from ghsa record GHSA-2x63-gw47-w4mm

  3. Revision 1 · created ·

    Published from ghsa record GHSA-2x63-gw47-w4mm

Agent brief

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# Patch Next advisory brief: CVE-2026-61666

Advisory: websocket-driver-ruby: Denial of service via malformed Host header
IDs: CVE-2026-61666, GHSA-2x63-gw47-w4mm
Record: https://patchnext.com/advisories/cve-2026-61666 (revision 3, source checked 3 Nov 2026, 06:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: websocket-driver 0.8.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems websocket-driver: affected < 0.8.2; fixed in 0.8.2

## Suggested inspection (read-only)
- RubyGems websocket-driver: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on websocket-driver.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2x63-gw47-w4mm (GitHub-reviewed advisory GHSA-2x63-gw47-w4mm lists affected ranges: RubyGems websocket-driver >=0 <0.8.2)
- Verified: https://osv.dev/vulnerability/GHSA-2x63-gw47-w4mm (OSV record GHSA-2x63-gw47-w4mm lists affected ranges: RubyGems websocket-driver >=0 <0.8.2 (fixed))

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