Vulnerability · Published Sep 15, 2026 · Assigned by GitHub_M

CVE-2026-69212Http4s: FollowRedirect middleware leaks credentials over https->http same-authority redirect

Medium 5.9

In plain English

A medium-severity information exposure in http4s from http4s. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)5.9Medium

Exploit odds (30 days)0.3%top 79.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack tooling1Public PoC

Official description

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.

Affected products (as reported)

Vendor	Product	Versions
http4s	http4s	< 0.23.35>= 1.0.0-M1, < 1.0.0-M47

Weakness: CWE-200, CWE-319 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References

https://github.com/http4s/http4s/security/advisories/GHSA-2rgg-r783-mrx4 x_refsource_CONFIRM
https://github.com/http4s/http4s/commit/6e825719b8d2f1538f2c49089c2dc81321a833b4 x_refsource_MISC
https://github.com/http4s/http4s/releases/tag/v0.23.35 x_refsource_MISC
https://github.com/http4s/http4s/releases/tag/v1.0.0-M47 x_refsource_MISC