nodejs undici up to 6.27.x/7.28.x/8.8.x Retry Interceptor improper synchronization

Summaryinfo

A vulnerability, which was classified as critical, was found in nodejs undici up to 6.27.x/7.28.x/8.8.x. This vulnerability affects unknown code of the component Retry Interceptor. The manipulation results in improper synchronization. This vulnerability was named CVE-2026-16728. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in nodejs undici up to 6.27.x/7.28.x/8.8.x. It has been classified as critical. Affected is some unknown functionality of the component Retry Interceptor. The manipulation with an unknown input leads to a improper synchronization vulnerability. CWE is classifying the issue as CWE-662. The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes. This is going to have an impact on integrity, and availability. CVE summarizes:

undici's retry interceptor can deliver a response whose body length does not match the Content-Length header exposed to the application after a retry or resume of a partial response. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a malicious or faulty upstream can return a partial response with a mismatched framing header, close the socket early, and have the retry interceptor assemble a body of a different length while the original Content-Length stays attached. Applications that use the retry interceptor and forward upstream headers and bodies downstream, such as proxies or gateways, may then emit an invalid HTTP response with a stale Content-Length, leading to downstream response desynchronization, connection hangs, or response corruption. Exploitation requires the retry interceptor enabled, an upstream returning a mismatched partial response, and a downstream forwarder that does not remove or recalculate Content-Length. The issue is fixed in undici 6.28.0, 7.29.0, and 8.9.0.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-16728 since 07/23/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are neither technical details nor an exploit publicly available.

Upgrading to version 6.28.0, 7.29.0 or 8.9.0 eliminates this vulnerability.

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Productinfo

Vendor

• nodejs

Name

• undici

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.7
• 6.8
• 6.9
• 6.10
• 6.11
• 6.12
• 6.13
• 6.14
• 6.15
• 6.16
• 6.17
• 6.18
• 6.19
• 6.20
• 6.21
• 6.22
• 6.23
• 6.24
• 6.25
• 6.26
• 6.27
• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5
• 7.6
• 7.7
• 7.8
• 7.9
• 7.10
• 7.11
• 7.12
• 7.13
• 7.14
• 7.15
• 7.16
• 7.17
• 7.18
• 7.19
• 7.20
• 7.21
• 7.22
• 7.23
• 7.24
• 7.25
• 7.26
• 7.27
• 7.28
• 8.0
• 8.1
• 8.2
• 8.3
• 8.4
• 8.5
• 8.6
• 8.7
• 8.8

Website

• Product: https://github.com/nodejs/undici/

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