GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

GHSA-JFWF-28XR-XW6Q

Vulnerability from github – Published: 2026-04-22 14:45 – Updated: 2026-05-20 01:35
VLAI
Summary
RClone: Unauthenticated operations/fsinfo allows attacker-controlled backend instantiation and local command execution
Details

Summary

The 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.

Preconditions

Preconditions for this vulnerability are:

  • The rclone remote control API must be enabled, either by the --rc flag or by running the rclone rcd server
  • 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
  • The rc must have been deployed without global RC HTTP authentication - so not using --rc-user/--rc-pass/--rc-htpasswd/etc

Details

The root cause consists of the following pieces:

  1. operations/fsinfo is not protected with AuthRequired: true
  2. operations/fsinfo calls rc.GetFs(...) on attacker-controlled input
  3. rc.GetFs(...) supports inline backend creation through object-valued fs
  4. WebDAV backend initialization executes bearer_token_command

Relevant code paths:

  • fs/operations/rc.go
  • operations/fsinfo is registered without AuthRequired: true

  • rcFsInfo() calls rc.GetFs(ctx, in)

  • fs/rc/cache.go

  • GetFs() / GetFsNamed() can parse an object-valued fs

  • getConfigMap() converts attacker-controlled JSON into a backend config string

  • backend/webdav/webdav.go

  • bearer_token_command is a supported backend option
  • NewFs(...) calls fetchAndSetBearerToken() when bearer_token_command is set
  • fetchBearerToken() invokes exec.Command(...)

This creates a practical single-request unauthenticated command-execution primitive on reachable RC servers without global HTTP authentication.

This was alidated on: - current master as of 2026-04-14: bf55d5e6d37fd86164a87782191f9e1ffcaafa82 - latest public release tested locally: v1.73.4

This was also validated on a public amd64 Ubuntu host controlled by the tester, using direct host execution (not containerized PoC execution).

PoC

Minimal single-request form PoC

Start a vulnerable RC server:

rclone rcd --rc-addr 127.0.0.1:5572

No --rc-user, no --rc-pass, no --rc-htpasswd.

Then send a single request:

curl -sS -X POST http://127.0.0.1:5572/operations/fsinfo \
  --data-urlencode "fs=:webdav,url='http://127.0.0.1/',vendor=other,bearer_token_command='/usr/bin/touch /tmp/rclone_fsinfo_rce_poc_marker':"

Expected result: - HTTP 200 JSON response from operations/fsinfo - /tmp/rclone_fsinfo_rce_poc_marker is created on the host

Impact

This is effectively a single-request unauthenticated command-execution vulnerability on reachable RC deployments without global HTTP authentication.

In 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.

Testing performed

This was successfully reproduced: - on a local test environment - on a public amd64 Ubuntu host controlled by the tester

On the public host it was confirmed:

  • the unauthenticated operations/fsinfo exploit worked
  • command execution occurred on the host
  • the issue was reproducible through direct host execution
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.2 (Critical)
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
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.73.4"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/rclone/rclone"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.48.0"
            },
            {
              "fixed": "1.73.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41179"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-306",
      "CWE-78"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T14:45:10Z",
    "nvd_published_at": "2026-04-23T00:16:45Z",
    "severity": "CRITICAL"
  },
  "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=\u0027http://127.0.0.1/\u0027,vendor=other,bearer_token_command=\u0027/usr/bin/touch /tmp/rclone_fsinfo_rce_poc_marker\u0027:\"\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",
  "id": "GHSA-jfwf-28xr-xw6q",
  "modified": "2026-05-20T01:35:40Z",
  "published": "2026-04-22T14:45:10Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "RClone: Unauthenticated operations/fsinfo allows attacker-controlled backend instantiation and local command execution"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.