Caddy Defender trusted proxy client IP bypass

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Summary

CVECVE-2026-46415
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-20 16:17:01 UTC
Updated2026-07-20 16:17:01 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 8.2 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Problem Types: CWE-284 | CWE-348 | CWE-284 CWE-284: Improper Access Control | CWE-348 CWE-348: Use of Less Trusted Source

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
3.1CNADECLARED8.2HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA JasonLovesDoggo Caddy-defender affected < 0.10.1 Not specified

References

ReferenceSourceLinkTags
github.com/JasonLovesDoggo/caddy-defender/pull/139 [email protected] github.com
github.com/JasonLovesDoggo/caddy-defender/security/advisories/GHSA-3h23-... [email protected] github.com
caddyserver.com/docs/caddyfile/options [email protected] caddyserver.com
caddyserver.com/docs/caddyfile/matchers [email protected] caddyserver.com
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