[ CVE-2026-18540 · Published 4 Sep 2026 ]
undici vulnerable to downstream response splitting via retry interceptor
[ Description ]Official description
undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.
[ Fixes ]Fixes and patches
- undici 6.28.1Fixed version · GitHub Advisories · npm package undici: upgrade to 6.28.1 or later (affected < 6.28.1)
- undici 7.29.1Fixed version · GitHub Advisories · npm package undici: upgrade to 7.29.1 or later (affected >= 7.0.0, < 7.29.1)
- undici 8.10.2Fixed version · GitHub Advisories · npm package undici: upgrade to 8.10.2 or later (affected >= 8.0.0, < 8.10.2)
[ Advisories ]Government CERT advisories
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CERT-FRCERTFR-2026-AVI-1336
Multiple vulnerabilities in IBM products Translated from French
Multiple vulnerabilities have been discovered in IBM products. Some of them allow an attacker to cause remote arbitrary code execution, privilege escalation and remote denial of service.
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BSI CERT-BundWID-SEC-2026-3596
IBM App Connect Enterprise: Multiple vulnerabilities Translated from German
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CERT-FRCERTFR-2026-AVI-1233
Multiple vulnerabilities in IBM products Translated from French
Multiple vulnerabilities have been discovered in IBM products. Some of them allow an attacker to cause remote arbitrary code execution, remote denial of service and a breach of data confidentiality.
[ Packages ]Affected open-source packages
- undici npmAffected < 6.28.1 · fixed in 6.28.1 · GHSA-r53p-7pc4-xj5r
- undici npmAffected >= 7.0.0, < 7.29.1 · fixed in 7.29.1 · GHSA-r53p-7pc4-xj5r
- undici npmAffected >= 8.0.0, < 8.10.2 · fixed in 8.10.2 · GHSA-r53p-7pc4-xj5r