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Response snapshot Nov 2, 2026, 22:11 UTC

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VulnerabilityCVE-2026-61666

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

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.

At a glance

Exploited
Not known
Severity
8.9 High (CVSS 4.0)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: websocket-driver: 0.8.2. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-2x63-gw47-w4mm (opens a new tab)

What happened

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.

Continue reading

Workarounds

No known workarounds exist.

Acknowledgements

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

Affected package ranges reported by GitHub: websocket-driver: < 0.8.2

Scores and how they were measured

CVSS base severity

8.9

Version 4.0As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-2x63-gw47-w4mm (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-2x63-gw47-w4mm, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, November 2). websocket-driver-ruby: Denial of service via malformed Host header (CVE-2026-61666). https://kevwire.com/record/CVE-2026-61666

MLA

"websocket-driver-ruby: Denial of service via malformed Host header (CVE-2026-61666)." KEVWire, 2 Nov. 2026, kevwire.com/record/CVE-2026-61666.

Chicago

KEVWire. "websocket-driver-ruby: Denial of service via malformed Host header (CVE-2026-61666)." Last modified November 2, 2026. https://kevwire.com/record/CVE-2026-61666.

Evidence summary (plain text)

websocket-driver-ruby: Denial of service via malformed Host header (Jul 21, 2026).
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.
CVSS 8.9 (version 4.0; evidence as of Nov 2, 2026; https://github.com/advisories/GHSA-2x63-gw47-w4mm).
Sources:
GitHub-reviewed advisory GHSA-2x63-gw47-w4mm: https://github.com/advisories/GHSA-2x63-gw47-w4mm
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-61666.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Nov 2, 2026, 22:10 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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