CVE-2026-61666Network attack vector

Server crash via uncaught Host parse error

Published Aug 17, 2026 · Updated Aug 17, 2026

Denial of service in Faye websocket-driver before 0.8.2 allows remote attackers to crash servers via a malformed Host header. In lib/websocket/http/request.rb, the request parser passes HTTP_HOST into URI.parse while deriving SERVER_NAME and SERVER_PORT and does not catch URI::InvalidURIError on malformed input. Exposure is limited to TCP-backed WebSocket servers that use WebSocket::Driver.server(); a single malformed upgrade request can terminate the process when the application leaves parse() exceptions unhandled.

CVSS severity8.9
High
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Faye websocket-driver before 0.8.2 allows remote attackers to crash servers via a malformed Host header. In lib/websocket/http/request.rb, the request parser passes HTTP_HOST into URI.parse while deriving SERVER_NAME and SERVER_PORT and does not catch URI::InvalidURIError on malformed input. Exposure is limited to TCP-backed WebSocket servers that use WebSocket::Driver.server(); a single malformed upgrade request can terminate the process when the application leaves parse() exceptions unhandled.

The record

CVE
CVE-2026-61666
Published
Aug 17, 2026
Updated
Aug 17, 2026
Vendor
Faye
Product
websocket-driver
Classifications
CWE-248, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 17, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.8.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Faye · websocket-driverversion=< 0.8.2

Published CVSS scores

8.9GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-248Uncaught Exception
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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