Time-of-check Time-of-use (TOCTOU) Race Condition in undici - CVE-2026-6733

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Main Vulnerability Database Vulnerabilities #VU134751

Time-of-check Time-of-use (TOCTOU) Race Condition in undici - CVE-2026-6733

Published: June 17, 2026


Vulnerability identifier: #VU134751
CSH Severity: Low
CVSS v4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-6733
CWE-ID: CWE-367
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to cause responses to be delivered to the wrong requests.

The vulnerability exists due to a time-of-check time-of-use race condition in the HTTP/1.1 client when reusing keep-alive sockets. A remote attacker can inject an unsolicited HTTP/1.1 response onto an idle socket to cause responses to be delivered to the wrong requests.

Exploitation requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse.


Affected software

undici
Netezza Appliance
Maximo Application Suite - Visual Inspection Component
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for Power, little endian
Fedora
nodejs22
nodejs24

How to mitigate CVE-2026-6733

Install security update from vendor's website.

undici - addressed in versions 6.26.0, 7.28.0, 8.5.0
Netezza Appliance - update to 1.0.2.0
Maximo Application Suite - Visual Inspection Component - addressed in versions 9.0.22, 9.1.19, 9.2.1
nodejs22 - update to 22.23.1-2.fc44
nodejs24 - update to 24.18.0-1.fc44

External References

Related Security Bulletins