Caddy: Remote Admin Authorization Bypass on PKI Endpoints via Prefix-Based Path Matching

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

AI Disclosure I used an LLM to help review the source code, reason about attack surface, and help draft and refine this report. I manually validated the finding by reproducing it locally, confirming the vulnerable code path, and verifying the HTTP behavior with curl -v.

Summary Caddy's remote admin access control performs path authorization using prefix matching: - admin.go: strings.HasPrefix(r.URL.Path, allowedPath) This allows a client certificate authorized only for /pki/ca/prod to access sibling PKI resources whose paths merely share the same prefix, such as /pki/ca/prod-backup. This is an authorization bug in Caddy's source code, not a misconfiguration issue. The configured policy is more restrictive than the behavior that Caddy actually enforces.

Affected Component Remote admin access control for PKI admin endpoints. Relevant code: - admin.go - admin.go - modules/caddypki/adminapi.go - modules/caddypki/adminapi.go

Root Cause In RemoteAdmin.enforceAccessControls(),…

Published by the source

19 May 2026, 19:36 UTC

Last modified by the source

19 May 2026, 19:36 UTC

Source last checked

26 Oct 2026, 15:22 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-gx7w-56w6-g48x

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# Patch Next advisory brief: GHSA-gx7w-56w6-g48x

Advisory: Caddy: Remote Admin Authorization Bypass on PKI Endpoints via Prefix-Based Path Matching
IDs: GHSA-gx7w-56w6-g48x
Record: https://patchnext.com/advisories/ghsa-gx7w-56w6-g48x (revision 1, source checked 26 Oct 2026, 15:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/caddyserver/caddy/v2 2.11.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/caddyserver/caddy/v2: affected < 2.11.3; fixed in 2.11.3

## Suggested inspection (read-only)
- Go github.com/caddyserver/caddy/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/caddyserver/caddy/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-gx7w-56w6-g48x (GitHub-reviewed advisory GHSA-gx7w-56w6-g48x lists affected ranges: Go github.com/caddyserver/caddy/v2 >=0 <2.11.3)

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