HTTP Response Splitting Affecting package, versions <2.29.1 >=2.30.0 <2.39.1 >=2.40.0 <2.42.0



    Attack Complexity Low

    Threat Intelligence

    EPSS 0.05% (15th percentile)
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7.5 high

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  • published 28 Sep 2022
  • disclosed 22 Aug 2022
  • credit Alessio Della Libera of Snyk Research Team

How to fix?

Upgrade apple/swift-nio to version 2.29.1, 2.39.1, 2.42.0 or higher.


apple/swift-nio is an event-driven network application framework for high performance protocol servers & clients, non-blocking.

Affected versions of this package are vulnerable to HTTP Response Splitting. This occurs when a HTTP/1.1 server accepts user generated input from an incoming request and reflects it into a HTTP/1.1 response header in some form. A malicious user can add newlines to their input (usually in encoded form) and "inject" those newlines into the returned HTTP response.

This capability allows users to work around security headers and HTTP/1.1 framing headers by injecting entirely false responses or other new headers. The injected false responses may also be treated as the response to subsequent requests, which can lead to XSS, cache poisoning, and a number of other flaws.

This issue was resolved by adding a default channel handler that polices outbound headers. This channel handler is added by default to channel pipelines, but can be removed by users if they are doing this validation themselves.