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

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

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.

undici
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Server for SAP Applications 12
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
openSUSE Leap
Fedora
Netezza Appliance
Maximo Application Suite - Visual Inspection Component
corepack16
nodejs16-docs
nodejs16-debuginfo
nodejs16-devel
npm16
nodejs16
nodejs16-debugsource
nodejs18-devel
npm18
nodejs18
nodejs18-debuginfo
nodejs18-debugsource
nodejs18-docs
corepack18
nodejs22
nodejs24

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
corepack16 - update to 16.20.2-150400.3.42.1
nodejs16-docs - update to 16.20.2-150400.3.42.1
nodejs16-debuginfo - update to 16.20.2-150400.3.42.1
nodejs16-devel - update to 16.20.2-150400.3.42.1
npm16 - update to 16.20.2-150400.3.42.1
nodejs16 - update to 16.20.2-150400.3.42.1
nodejs16-debugsource - update to 16.20.2-150400.3.42.1
nodejs18-devel - addressed in versions 18.20.8-8.44.1, 18.20.8-150400.9.39.1
npm18 - addressed in versions 18.20.8-8.44.1, 18.20.8-150400.9.39.1
nodejs18 - addressed in versions 18.20.8-8.44.1, 18.20.8-150400.9.39.1
nodejs18-debuginfo - addressed in versions 18.20.8-8.44.1, 18.20.8-150400.9.39.1
nodejs18-debugsource - addressed in versions 18.20.8-8.44.1, 18.20.8-150400.9.39.1
nodejs18-docs - addressed in versions 18.20.8-8.44.1, 18.20.8-150400.9.39.1
corepack18 - update to 18.20.8-150400.9.39.1
nodejs22 - update to 22.23.1-2.fc44
nodejs24 - update to 24.18.0-1.fc44

• https://github.com/nodejs/undici/security/advisories/GHSA-35p6-xmwp-9g52
• https://hackerone.com/reports/3582376

• Multiple vulnerabilities in undici
• Multiple vulnerabilities in IBM Maximo Application Suite - Visual Inspection Component
• Multiple vulnerabilities in IBM Netezza Appliance
• Fedora 44 update for nodejs24
• Fedora 44 update for nodejs22
• Red Hat Enterprise Linux 9 update for the nodejs:24 module
• Red Hat Enterprise Linux 9 update for the nodejs:22 module
• Red Hat Enterprise Linux 8 update for the nodejs:24 module
• Red Hat Enterprise Linux 8 update for the nodejs:22 module
• SUSE update for nodejs18
• SUSE update for nodejs18
• SUSE update for nodejs16