Http4s: FollowRedirect middleware leaks credentials over https->http same-authority redirect

Http4s: FollowRedirect middleware leaks credentials over https->http same-authority redirect

Http4s is a Scala interface for HTTP services. Prior to 0.23.35 and 1.0.0-M47, The FollowRedirect client middleware strips Authorization and Cookie headers only when a redirect changes authority, but authority comparison excludes the URI scheme. A same-authority redirect from HTTPS to HTTP therefore preserves credentials and transmits them over a plaintext connection. An attacker who can induce the downgrade and observe the network can capture those sensitive headers from applications using FollowRedirect. This issue is fixed in versions 0.23.35 and 1.0.0-M47.

Source published

15 Sep 2026 19:09:57 UTC

Source modified

15 Sep 2026 19:30:41 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVE Program Terms of Use

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CVSS 3.1 · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N