CVE-2026-69212 Http4s: FollowRedirect middleware leaks credentials over https->http same-authority redirect
Attackers can capture sensitive credentials transmitted over plaintext HTTP due to a flaw in Http4s FollowRedirect middleware handling same-authority downgrades.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-69212?
CVE-2026-69212 is a medium-severity vulnerability in http4s, published on 15 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-69212?
How do I fix CVE-2026-69212?
No fix has been published for CVE-2026-69212 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-69212 being exploited?
There is no known exploitation of CVE-2026-69212 in the wild and no public exploit code.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-2rgg-r783-mrx4.