CVE-2026-105766: Chainguard Academy (edu) Nginx directory redirect downgrades HTTPS requests to HTTP
Use of the backend-facing $scheme variable in the trailing-slash directory redirect in nginx.conf of Chainguard Academy (edu) from commit 0b75ff98057f69b044a3e7194e428066ac5ad0d4 before commit 93dc0e50739c225f5aee2e803800a47fc0feb906 allows an on-path network attacker to read or modify documentation content served to a victim via an HTTPS request for a slashless directory path, because TLS terminates at the load balancer in front of Nginx and the resulting 301 response redirects the client to a plaintext http:// URL. Browsers that ship the HSTS preload list are not affected, because the .dev top-level domain is preloaded; clients that do not enforce HSTS, such as command-line HTTP clients and scripts that follow redirects, are affected.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Chainguard Academy (edu) Nginxto a version that resolves this vulnerability.Patch 93dc0e50739c225f5aee2e803800a47fc0feb906
Event History
Frequently Asked Questions
Which clients are realistically exposed to this redirect downgrade?
Clients that do not enforce HSTS are affected, including command-line HTTP clients and scripts that automatically follow redirects. Browsers with the HSTS preload list are not affected because the .dev top-level domain is preloaded.
What conditions must an attacker meet to exploit the issue?
A victim must request a directory path without its trailing slash over HTTPS and follow the resulting redirect. An attacker must be positioned on the network path to intercept the redirected plaintext HTTP request, allowing them to read or modify the documentation content.
Which versions or revisions are affected?
The issue affects Chainguard Academy (edu) from commit 0b75ff98057f69b044a3e7194e428066ac5ad0d4 up to, but not including, commit 93dc0e50739c225f5aee2e803800a47fc0feb906.