CVE-2026-46415
HighCVSS 8.2Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
The Caddy Defender plugin before version 0.10.1 used `r.RemoteAddr` instead of the resolved client IP (`client_ip`) for request blocking. In deployments behind a trusted proxy, CDN, or load balancer, `RemoteAddr` points to the proxy's address, allowing attackers from blocked IP ranges to bypass the blocking rules.
Risk Assessment
Organizations using Caddy Defender behind a trusted proxy are at risk of IP blocking bypass, potentially leading to unauthorized access, DDoS attacks, or other threats that the plugin was intended to mitigate.
Recommendation
Upgrade Caddy Defender to version 0.10.1 or later immediately. Until upgraded, enforce equivalent IP blocking at the trusted proxy, firewall, or other edge layer before traffic reaches Caddy.
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Original NVD description (English source)
The Caddy Defender plugin is a middleware for Caddy that allows users to block or manipulate requests based on the client's IP address. Prior to version 0.10.1, Caddy Defender used `r.RemoteAddr` when evaluating whether a request should be blocked. `RemoteAddr` is the address of the immediate peer connected to Caddy. In deployments where Caddy is behind a trusted proxy, CDN, or load balancer, the immediate peer is usually the proxy, not the original client. Caddy resolves the original client address into its `client_ip` request variable after applying the configured `trusted_proxies` policy, but Defender did not use that value. As a result, clients from blocked IP ranges could bypass Defender when accessing Caddy through a trusted proxy whose own IP address was not blocked. This affects deployments that use Defender behind trusted proxies and expect it to enforce blocking based on the real client IP. The issue is fixed in version 0.10.1 by making Defender prefer Caddys resolved `client_ip` request variable when it is available. Defender falls back to `RemoteAddr` only when Caddy has not provided a resolved client IP. There is no complete workaround in affected Defender versions for deployments that rely on Caddy's trusted proxy client IP resolution. Until upgrading, affected users should enforce equivalent IP blocking at the trusted proxy, CDN, load balancer, firewall, or other edge layer before traffic reaches Caddy. Deployments where Caddy receives traffic directly from clients, without an intermediate trusted proxy, are not affected by this bypass.