CVE-2023-49783

Executive Summary

CVE-2023-49783 is a missing authorization vulnerability in the Silverstripe Admin module, affecting versions prior to 1.13.19 (1.x branch) and 2.1.8 (2.x branch). The flaw allows authenticated users with only "create" permissions on a ModelAdmin to bypass edit and delete restrictions via the CSV import form. By crafting a malicious CSV file, an attacker can modify or remove records they should not have access to, leading to unauthorized data manipulation. The vulnerability has a low CVSS score of 4.3 due to the prerequisite of having create permissions, but it poses a significant risk in environments where role separation is critical.

Supply Chain & Package Security

This vulnerability affects the Silverstripe Admin package, which is distributed via Composer (PHP). The package is a core component of the Silverstripe CMS ecosystem. Users should verify their composer.json for the silverstripe/admin package and ensure it is updated to a patched version. No known supply chain attacks have been reported, but the risk of dependency confusion or malicious forks exists if the package is mirrored.

CVSS Breakdown & Threat Level

• CVSS Score: 4.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (create permission)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: Low
• Availability Impact: None

The threat level is considered medium due to the low likelihood of an attacker having create permissions without edit/delete permissions. However, in misconfigured environments, this can lead to data integrity breaches.

Deep Dive & Mechanics

The vulnerability resides in the CSV import functionality of ModelAdmin. The BulkLoader class, which processes CSV imports, does not enforce edit or delete permissions when the user has create permissions. The getCheckPermissions() method is intended to control permission checks, but by default it returns false, meaning no checks are performed. Even when set to true, the implementation in BulkLoader does not properly validate the user's ability to edit or delete existing records.

The attack flow:

1. An attacker with create permissions on a ModelAdmin (e.g., a content editor who can add new articles but not edit or delete others' articles) accesses the CSV import form.
2. The attacker crafts a CSV file containing records with existing IDs (to edit) or records to delete (via a special delete flag).
3. The BulkLoader processes the CSV and performs edit/delete operations without checking if the user has the required permissions.
4. The attacker successfully modifies or removes records they should not have access to.

Vulnerable vs. Patched Code

Vulnerable Code (BulkLoader.php):

public function getCheckPermissions() {
    return false; // Default: no permission checks
}

public function load($filepath) {
    // ... process CSV ...
    if ($this->getCheckPermissions()) {
        // Permission check is missing for edit/delete operations
    }
    // ... perform edit/delete ...
}

Patched Code (BulkLoader.php):

public function getCheckPermissions() {
    return true; // Now defaults to true
}

public function load($filepath) {
    // ... process CSV ...
    if ($this->getCheckPermissions()) {
        $member = Security::getCurrentUser();
        foreach ($records as $record) {
            if ($record->isInDB()) {
                if (!$record->canEdit($member) && !$record->canDelete($member)) {
                    throw new PermissionFailureException('...');
                }
            }
        }
    }
    // ... perform edit/delete ...
}

The patch ensures that when getCheckPermissions() returns true, the BulkLoader checks the user's edit and delete permissions before processing existing records.

Exploitation & Lab Setup

Red Team

To exploit this vulnerability, an attacker needs:

• A valid session with create permissions on a ModelAdmin.
• Access to the CSV import form (typically at /admin/<model>/import).

Step-by-step exploitation:

1. Log in as a user with create permissions.
2. Navigate to the CSV import form for the target model.
3. Craft a CSV file with the following structure:

   ID,Title,Content
   1,Modified Title,Modified Content
   

   For deletion, use a special flag (e.g., Delete column with value 1).
4. Upload the CSV file. The BulkLoader will process it and modify/delete records without permission checks.

Lab Setup:

• Install Silverstripe 2.1.0 (vulnerable) using Composer: composer create-project silverstripe/installer myapp 2.1.0
• Create a ModelAdmin with a custom model.
• Assign a user with only create permissions.
• Access the import form and upload a malicious CSV.

Blue Team

Detection:

• Monitor CSV import logs for unusual patterns (e.g., imports by users with limited permissions).
• Check for bulk modifications or deletions of records by users who should not have edit/delete rights.
• Use the detection rules below to identify exploitation attempts.

Mitigation:

• Immediately update to patched versions (1.13.19 or 2.1.8).
• If patching is not possible, disable the CSV import form by setting showImportForm = false in ModelAdmin.
• Review and restrict create permissions to only trusted users.

Indicators of Compromise (IOCs)

• Log Entries: CSV import events from users with only create permissions.
• File Artifacts: Malicious CSV files uploaded to the server (check /tmp or upload directories).
• Database Changes: Unexpected modifications or deletions of records that should be protected.
• Network Traffic: POST requests to /admin/<model>/import with Content-Type: multipart/form-data containing CSV data.

Detection Engineering

YARA Rule

rule CVE_2023_49783_CSV_Import_Abuse {
    meta:
        description = "Detects CSV files attempting to exploit CVE-2023-49783"
        author = "Valters IT"
        date = "2025-04-17"
        reference = "CVE-2023-49783"
    strings:
        $csv_header = /ID,.*/ nocase
        $delete_flag = /Delete,1/ nocase
    condition:
        $csv_header and $delete_flag
}

Sigma Rule

title: CVE-2023-49783 - CSV Import Permission Bypass
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects CSV import requests from users with limited permissions
author: Valters IT
date: 2025-04-17
logsource:
    category: application
    product: silverstripe
detection:
    selection:
        EventID: 1001  # Custom event for CSV import
        UserPermissions: "create"
        Action: "import"
    condition: selection
falsepositives:
    - Legitimate imports by users with create permissions who also have edit/delete permissions
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2023-49783 - CSV Import Attempt"; flow:to_server; content:"POST"; http_method; content:"/admin/"; http_uri; content:"import"; http_uri; content:"multipart/form-data"; http_header; content:".csv"; file_data; pcre:"/ID,/"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Update Silverstripe Admin to version 1.13.19 (1.x) or 2.1.8 (2.x) using Composer:

   composer require silverstripe/admin:^1.13.19  # For 1.x
   composer require silverstripe/admin:^2.1.8   # For 2.x
   

2. If patching is delayed, disable the CSV import form in all ModelAdmin classes:

   class MyModelAdmin extends ModelAdmin {
       private static $showImportForm = false;
   }
   

3. Review all custom BulkLoader implementations and ensure they call setCheckPermissions(true) and properly validate permissions.

Long-term Measures:

• Implement role-based access control (RBAC) with least privilege principles.
• Regularly audit user permissions, especially create permissions.
• Enable logging for all import operations and monitor for anomalies.
• Conduct security training for developers on proper permission checks in custom BulkLoader implementations.

Valters IT
Securing Digital Frontiers