CVE-2026-41179: RClone Unauthenticated Operations/fsinfo Allows Attacker-controlled Backend Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jfwf-28xr-xw6q",
  "modified" : "2026-05-20T01:35:40Z",
  "published" : "2026-04-22T14:45:10Z",
  "aliases" : [ "CVE-2026-41179" ],
  "summary" : "RClone: Unauthenticated operations/fsinfo allows attacker-controlled backend instantiation and local command execution",
  "details" : "### Summary\nThe RC endpoint `operations/fsinfo` is exposed without `AuthRequired: true` and accepts attacker-controlled `fs` input. Because `rc.GetFs(...)` supports inline backend definitions, an unauthenticated attacker can instantiate an attacker-controlled backend on demand. For the WebDAV backend, `bearer_token_command` is executed during backend initialization, making single-request unauthenticated local command execution possible on reachable RC deployments without global HTTP authentication.\n\n### Preconditions\n\nPreconditions for this vulnerability are:\n\n- The rclone remote control API **must** be enabled, either by the `--rc` flag or by running the `rclone rcd` server\n- The remote control API **must** be reachable by the attacker - by default rclone only serves the rc to localhost unless the `--rc-addr` flag is in use\n- The rc must have been deployed **without** global RC HTTP authentication - so not using `--rc-user`/`--rc-pass`/`--rc-htpasswd`/etc\n\n\n### Details\nThe root cause consists of the following pieces:\n\n1. `operations/fsinfo` is not protected with `AuthRequired: true`\n2. `operations/fsinfo` calls `rc.GetFs(...)` on attacker-controlled input\n3. `rc.GetFs(...)` supports inline backend creation through object-valued `fs`\n4. WebDAV backend initialization executes `bearer_token_command`\n\nRelevant code paths:\n\n- [`fs/operations/rc.go`](https://github.com/rclone/rclone/blob/bf55d5e6d37fd86164a87782191f9e1ffcaafa82/fs/operations/rc.go)\n  - `operations/fsinfo` is registered without `AuthRequired: true`\n  - `rcFsInfo()` calls `rc.GetFs(ctx, in)`\n\n- [`fs/rc/cache.go`](https://github.com/rclone/rclone/blob/bf55d5e6d37fd86164a87782191f9e1ffcaafa82/fs/rc/cache.go)\n  - `GetFs()` / `GetFsNamed()` can parse an object-valued `fs`\n  - `getConfigMap()` converts attacker-controlled JSON into a backend config string\n\n- [`backend/webdav/webdav.go`](https://github.com/rclone/rclone/blob/bf55d5e6d37fd86164a87782191f9e1ffcaafa82/backend/webdav/webdav.go)\n  - `bearer_token_command` is a supported backend option\n  - `NewFs(...)` calls `fetchAndSetBearerToken()` when `bearer_token_command` is set\n  - `fetchBearerToken()` invokes `exec.Command(...)`\n\nThis creates a practical single-request unauthenticated command-execution primitive on reachable RC servers without global HTTP authentication.\n\nThis was alidated on:\n- current `master` as of 2026-04-14: `bf55d5e6d37fd86164a87782191f9e1ffcaafa82`\n- latest public release tested locally: `v1.73.4`\n\nThis was also validated on a public amd64 Ubuntu host controlled by the tester, using direct host execution (not containerized PoC execution).\n\n### PoC\n#### Minimal single-request form PoC\nStart a vulnerable RC server:\n\n```bash\nrclone rcd --rc-addr 127.0.0.1:5572\n```\n\nNo `--rc-user`, no `--rc-pass`, no `--rc-htpasswd`.\n\nThen send a single request:\n\n```bash\ncurl -sS -X POST http://127.0.0.1:5572/operations/fsinfo \\\n  --data-urlencode \"fs=:webdav,url='http://127.0.0.1/',vendor=other,bearer_token_command='/usr/bin/touch /tmp/rclone_fsinfo_rce_poc_marker':\"\n```\n\nExpected result:\n- HTTP 200 JSON response from `operations/fsinfo`\n- `/tmp/rclone_fsinfo_rce_poc_marker` is created on the host\n\n### Impact\nThis is effectively a single-request unauthenticated command-execution vulnerability on reachable RC deployments without global HTTP authentication.\n\nIn practice, command execution in the rclone process context can lead to higher-impact outcomes such as local file read, file write, or shell access, depending on the deployed environment.\n\n#### Testing performed\nThis was successfully reproduced:\n- on a local test environment\n- on a public amd64 Ubuntu host controlled by the tester\n\nOn the public host it was confirmed:\n\n- the unauthenticated `operations/fsinfo` exploit worked\n- command execution occurred on the host\n- the issue was reproducible through direct host execution",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rclone/rclone"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.48.0"
      }, {
        "fixed" : "1.73.5"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.73.4"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rclone/rclone/security/advisories/GHSA-jfwf-28xr-xw6q"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41179"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rclone/rclone/commit/2a9e952b38e03a96bf40c9eb6e8e22199865ee3b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rclone/rclone"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rclone/rclone/blob/bf55d5e6d37fd86164a87782191f9e1ffcaafa82/backend/webdav/webdav.go"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rclone/rclone/blob/bf55d5e6d37fd86164a87782191f9e1ffcaafa82/fs/operations/rc.go"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rclone/rclone/blob/bf55d5e6d37fd86164a87782191f9e1ffcaafa82/fs/rc/cache.go"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rclone/rclone/releases/tag/v1.73.5"
  }, {
    "type" : "WEB",
    "url" : "https://rclone.org/changelog/#v1-73-5-2026-04-19"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306", "CWE-78" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-22T14:45:10Z",
    "nvd_published_at" : "2026-04-23T00:16:45Z"
  }
}