Uncaught Exception in undici - CVE-2026-19534
Published: September 6, 2026
Vulnerability identifier: #VU147180
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-19534
CWE-ID: CWE-248
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to an uncaught exception in the undici WebSocket client opening handshake when processing a server response containing an unrequested Sec-WebSocket-Protocol header. A remote attacker can send a crafted WebSocket handshake response to cause a denial of service.
Exploitation requires an application to open a WebSocket connection to an attacker-controlled or compromised server, or to use a plaintext ws:// connection subject to a machine-in-the-middle.
Affected software
undici
How to mitigate CVE-2026-19534
Install security update from vendor's website.
undici - addressed in versions 6.28.1, 7.29.1, 8.10.2