Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, the local caddy admin API (default listen 127.0.0.1:2019) exposes a state-changing POST /load endpoint that replaces the entire running configuration. When origin enforcement is not enabled (enforce_origin not configured), the admin endpoint accepts cross-origin requests (e.g., from attacker-controlled web content in a victim browser) and applies an attacker-supplied JSON config. This can change the admin listener settings and alter HTTP server behavior without user intent. Version 2.11.1 contains a fix for the issue.
Exploitability
AV:NAC:LAT:PPR:NUI:NVulnerable System
VC:NVI:HVA:NSubsequent System
SC:NSI:NSA:N6.9/CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:PAuthentication