CVE-2026-61666

HIGHCVSS · not yet scored
—
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • No CVSS published and no exploitation signals yet
CISA-KEV: Not listedEPSS PROB: —CVSS v2: —Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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

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.

CVSS v3
—
EG Score
0.0(none)
EG Risk
0
EG Risk 0/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses intrinsic severity with real-world exploitation and automatability, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. It is distinct from the 0–10 EG Score, which measures severity.

EPSS PROB
—
EPSS %ILE
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KEV
Not listed

Published

July 21, 2026

Last Modified

July 21, 2026

Vendor Advisories for CVE-2026-61666(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
websocket-driver0.1.0 ... 0.8.1 (33 versions)0.8.2—

Data Freshness Timeline

(refreshed 3× in last 7d / 3× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-26 10:29 UTCEG score recompute
  2. 2026-07-23 03:21 UTCEG score recompute
  3. 2026-07-21 19:19 UTCEG score recompute

Frequently asked(3)

What is CVE-2026-61666?
CVE-2026-61666 is a high vulnerability published on July 21, 2026. websocket-driver-ruby: Denial of service via malformed Host header 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…
When was CVE-2026-61666 disclosed?
CVE-2026-61666 was first published in the National Vulnerability Database on July 21, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
How do I remediate CVE-2026-61666?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-61666, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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