CVE-2026-19534: Red Hat Denial of Service via unrequested WebSocket subprotocol
This Red Hat advisory covers CVE-2026-19534 in Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 and Red Hat Enterprise Linux 9.
Key facts
- Vendor rating
- High, CVSS 7.5
- CISA KEV
- Not listed (catalogue checked )
- Affected
- 6.7.0; 7.0.0; 8.0.0
- Fixed in
- 6.28.1, 7.29.1, 8.10.2 and 38 more below
- Source published
- Listed by VulniPulse
Compiled by VulniPulse from the linked sources. How records are collected and checked.
Affected products & platforms
Description
undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested.
A default WebSocket connection sends no subprotocol, but if the server's 101 response includes a Sec-WebSocket-Protocol header, undici dereferences a null value while checking it against the requested list and throws an uncaught TypeError.
Because that code runs inside a microtask with no surrounding error handling, the exception propagates and terminates the process under Node's default behavior, instead of gracefully failing the connection as required by the WebSocket protocol.
Any application that opens a WebSocket to an attacker-controlled or compromised server, or over a plaintext connection subject to a machine-in-the-middle, can be crashed remotely without authentication in the default configuration. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.
A flaw was found in undici. A remote attacker can exploit this vulnerability by responding with an unrequested WebSocket subprotocol during the opening handshake.
This causes the undici WebSocket client to crash the entire Node.js process, leading to a denial of service (DoS).
Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Cluster Observability Operator 1.5.3; and 16 more.
Text from the source record.
- 6.7.0
- 7.0.0
- 8.0.0
Official advisory · high-confidence parse· fetched ·verify at source
How to fix CVE-2026-19534
Upgrade to a fixed release named by Red Hat:
- 6.28.1
- 7.29.1
- 8.10.2
- nodejs24-1:24.21.0-1.el10_2
- nodejs22-1:22.23.2-3.el10_2
- nodejs:24-8100020260921144227.6d880403
- nodejs:22-8100020260928121333.6d880403
- nodejs:24-9080020260921144317.rhel9
- nodejs:22-9080020260928121441.rhel9
- cluster-observability-operator/logging-console-plugin-pf4-rhel9:1790854525
- cluster-observability-operator/monitoring-console-plugin-pf5-rhel9:1790854526
- cluster-observability-operator/monitoring-console-plugin-pf6-rhel9:1790854528
- cluster-observability-operator/monitoring-console-plugin-rhel9:1790854525
- ansible-automation-platform/automation-portal:1790254963
- ansible-automation-platform/automation-portal:1790256405
- rhdh/red-hat-developer-hub-backstage-plugin-lightspeed-backend:1791242697
- rhdh/red-hat-developer-hub-backstage-plugin-orchestrator-backend:1791251282
- rhdh/red-hat-developer-hub-backstage-plugin-orchestrator-backend-module-loki:1791250355
- rhdh/red-hat-developer-hub-backstage-plugin-scaffolder-backend-module-orchestrator:1791249640
- rhdh/rhdh-hub-rhel9:1791311495
- rhdh/rhdh-hub-rhel9:1789554285
- grafana12-4-main-12.4.10-0.2.hum1
- nodejs26-main-11.19.1-1.26.8.2.0.1.hum1
- nodejs26-main-26.8.2-0.1.hum1
- nodejs24-main-11.19.0-1.24.21.0.1.hum1
and 16 more in the Red Hat advisory.
Vendor guidance
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Support dates for the fixed release lines
- Red Hat Enterprise Linux 6: support ended
- Red Hat Enterprise Linux 7: support ended
- Red Hat Enterprise Linux 8: support ends
CVE-2026-19534 in other vendors' advisories
- Atlassian: CVE-2026-19534, high severity, fixed in Jira Data Center and Server: 11.3.12 (LTS) recommended Data Center Only, Jira Data Center and Server: 10.3.26 (LTS) Data Center Only, Jira Service Management Data Center and Server: 11.3.12 (LTS) recommended Data Center Only and 1 more
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