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Vulnerability record · CVE-2026-6733 · published 17 June 2026

CVE-2026-6733: Nodejs undici toctou race condition vulnerability

Nodejs · Undici

Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests. This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse. Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0. Workarounds: Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.

3.7 CVSS 3.1 Low EPSS 0.27% · top 82.4% CWE-367 · TOCTOU race condition
3.7CVSS 3.1 base score
0.27%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
27 Jun 2026Last modified by NVD

Description

Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests. This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse. Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0. Workarounds: Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://cna.openjsf.org/security-advisories.html Vendor Advisory
https://github.com/nodejs/undici/security/advisories/GHSA-35p6-xmwp-9g52 MitigationVendor Advisory
https://hackerone.com/reports/3582376 Issue Tracking

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-6733), CISA KEV, FIRST EPSS (scores of 2026-10-07). This page is refreshed as NVD updates the record.