CVE-2026-61666: websocket-driver-ruby Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-2x63-gw47-w4mm
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CWE-248
Published
Advisory Summary

CVE-2026-61666 is a HIGH denial of service vulnerability (CWE-248: Uncaught Exception) affecting websocket-driver-ruby libraries in the RubyGems ecosystem. The issue involves denial of service via malformed host header. Remediation is available by upgrading affected packages to version 0.8.2.

CVE-2026-61666 at a Glance

CVE Identifier CVE-2026-61666
GHSA Identifier GHSA-2x63-gw47-w4mm
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-248: Uncaught Exception
Affected Product websocket-driver-ruby
Package Ecosystem RubyGems
Published Date
Last Updated

How to Fix CVE-2026-61666

To remediate this vulnerability, upgrade all affected websocket-driver-ruby dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

websocket-driver fixed: 0.8.2 
Upgrade websocket-driver to 0.8.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for websocket-driver

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-61666, inspect your project dependencies for websocket-driver-ruby:

inspect dependencies for websocket-driver

Analyze the terminal output to locate any version of websocket-driver-ruby in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.8.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-248: Uncaught Exception, where an exception is thrown from a function, but it is not caught. In websocket-driver-ruby, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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.

CVE-2026-61666 Affected websocket-driver-ruby Versions

1 component(s)
Fixed Versions:
0.8.2
Product / Package Ecosystem Affected Versions Fixed Version
websocket-driver
gem/websocket-driver
RubyGems
< 0.8.2
0.8.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/faye/websocket-driver-ruby/security/advisories/GHSA-2x63-gw47-w4mm
Security Fix Commit FIX COMMIT
https://github.com/faye/websocket-driver-ruby/commit/7d6fd87759a2fdc83590d3b49ffa661dc53fa128
websocket-driver-ruby Source Repository REPOSITORY
https://github.com/faye/websocket-driver-ruby

Frequently Asked Questions

What is CVE-2026-61666?
CVE-2026-61666 is a security vulnerability in websocket-driver-ruby involving Denial of service via malformed Host header under CWE-248: Uncaught Exception.
Which websocket-driver-ruby versions are affected?
Affected versions include releases prior to 0.8.2 across affected packages: websocket-driver.
What version fixes CVE-2026-61666?
Upgrading to 0.8.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is websocket-driver affected?
Yes, websocket-driver is affected in releases prior to 0.8.2. Upgrade your dependency to 0.8.2 or later.
What CWE is associated with CVE-2026-61666?
CVE-2026-61666 is classified under CWE-248: Uncaught Exception (An exception is thrown from a function, but it is not caught.).
How can I check RubyGems dependencies for CVE-2026-61666?
Run the dependency tree command: 'inspect dependencies for websocket-driver'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2x63-gw47-w4mm",
  "modified" : "2026-07-21T18:34:42Z",
  "published" : "2026-07-21T18:34:42Z",
  "aliases" : [ "CVE-2026-61666" ],
  "summary" : "websocket-driver-ruby: Denial of service via malformed Host header",
  "details" : "### Impact\n\nIf 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.\n\n### Patches\n\nThe 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.\n\n### Workarounds\n\nNo known workarounds exist.\n\n### Acknowledgements\n\nThis issue was discovered and reported by Pranjali Thakur, DepthFirst Security Research Team.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "websocket-driver"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.8.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/faye/websocket-driver-ruby/security/advisories/GHSA-2x63-gw47-w4mm"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/faye/websocket-driver-ruby/commit/7d6fd87759a2fdc83590d3b49ffa661dc53fa128"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/faye/websocket-driver-ruby"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-248" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-21T18:34:42Z",
    "nvd_published_at" : null
  }
}