Npm · Undici · CVE-2026-18540
**Name of the Vulnerable Software and Affected Versions**
undici versions prior to 6.28.1
undici versions 7.0.0 through 7.29.1
undici versions 8.0.0 through 8.10.2
**Description**
The retry interceptor can append the body of a ranged retry response to bytes already delivered from a previous partial response while maintaining the original response status and headers. This occurs when an upstream server provides part of a body without a trustworthy resume checkpoint—such as a non-success response with already sent headers or a partial-content response with an unusable content range—closes the connection, and then provides more bytes in the resumed range request. Consequently, the response body may exceed the `Content-Length` observed by the application. If an application relays this response to a downstream HTTP/1.1 peer without normalizing the framing, the excess bytes may be interpreted as the start of a subsequent response, leading to downstream response splitting or desynchronization. This requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path.
**Recommendations**
Update to version 6.28.1 for versions prior to 6.28.1.
Update to version 7.29.1 for versions 7.0.0 through 7.29.1.
Update to version 8.10.2 for versions 8.0.0 through 8.10.2.