CVE-2023-51644

Executive Summary

CVE-2023-51644 is a critical remote code execution vulnerability in Allegra, a project management and collaboration platform. The flaw resides in the SiteConfigAction component, which improperly handles access control within the Struts framework. An unauthenticated attacker can exploit this to execute arbitrary code in the context of the LOCAL SERVICE account, leading to full system compromise. With a CVSS score of 9.8, this vulnerability poses a severe risk to affected installations. No public proof-of-concept or patch is currently available, but the vulnerability has been disclosed via ZDI (ZDI-CAN-22512).

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects the Allegra application directly, which is a proprietary software product. Organizations using Allegra should treat this as a critical supply chain risk and monitor for vendor updates.

CVSS Breakdown & Threat Level

• CVSS Score: 9.8 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

The vulnerability allows unauthenticated remote attackers to execute arbitrary code, making it trivial to exploit and devastating in impact.

Deep Dive & Mechanics

The vulnerability exists in the SiteConfigAction class of Allegra, which is part of the Struts framework. The issue stems from improper access control—the action does not enforce authentication or authorization checks before processing requests. An attacker can send a crafted HTTP request to the vulnerable endpoint, which triggers the execution of arbitrary code due to insecure deserialization or direct object manipulation within Struts.

The specific flaw likely involves Struts’ dynamic method invocation or parameter binding, where an attacker can manipulate input parameters to invoke arbitrary methods or instantiate arbitrary classes. This leads to remote code execution in the context of the LOCAL SERVICE account, which has elevated privileges on the system.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the SiteConfigAction class. A patched version would require:

• Adding authentication checks (e.g., @RequiresAuthentication annotation).
• Validating user permissions before processing actions.
• Implementing input validation and whitelisting for Struts parameters.

Example of vulnerable code (conceptual):

public class SiteConfigAction extends ActionSupport {
    public String execute() {
        // No access control check
        String config = request.getParameter("config");
        // Process config without validation
        return SUCCESS;
    }
}

Patched code (conceptual):

public class SiteConfigAction extends ActionSupport {
    @RequiresAuthentication
    @RequiresPermission("admin")
    public String execute() {
        String config = request.getParameter("config");
        if (!isValidConfig(config)) {
            return ERROR;
        }
        // Process config safely
        return SUCCESS;
    }
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Target running Allegra with vulnerable SiteConfigAction.
• No authentication required.

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., /SiteConfigAction.action).
2. Craft a malicious HTTP request with a payload that exploits Struts’ parameter binding or OGNL injection.
3. Send the request to execute arbitrary commands.

Example payload (conceptual):

POST /SiteConfigAction.action HTTP/1.1
Host: target.com
Content-Type: application/x-www-form-urlencoded

config=@java.lang.Runtime@getRuntime().exec("cmd /c calc.exe")

Note: No public exploit code is available; this is a conceptual example.

Blue Team

Detection:

• Monitor for unusual HTTP requests to /SiteConfigAction.action or similar Struts endpoints.
• Look for OGNL expressions or Java class references in POST parameters.
• Alert on processes spawned by the LOCAL SERVICE account that are not typical.

Hunting:

• Search logs for SiteConfigAction with parameters containing @, Runtime, or exec.
• Use YARA rules to scan for malicious payloads in web logs.

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to /SiteConfigAction.action with suspicious parameters.
  • Outbound connections from the LOCAL SERVICE account to external IPs.
• File:
  • Unexpected files written to %WINDIR%\Temp or %PROGRAMDATA%.
  • New executables or scripts in the Allegra installation directory.
• Process:
  • cmd.exe, powershell.exe, or wscript.exe spawned by AllegraService.exe or similar.
• Registry:
  • Unauthorized modifications to HKLM\SYSTEM\CurrentControlSet\Services.

Detection Engineering

YARA Rule

rule CVE_2023_51644_Allegra_RCE {
    meta:
        description = "Detects exploitation attempts for CVE-2023-51644 in Allegra"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2023-51644"
    strings:
        $s1 = "SiteConfigAction" ascii wide nocase
        $s2 = "Runtime" ascii wide nocase
        $s3 = "exec" ascii wide nocase
        $s4 = "getRuntime" ascii wide nocase
    condition:
        all of ($s*) and filesize < 10KB
}

Sigma Rule

title: CVE-2023-51644 Allegra RCE Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP requests targeting Allegra SiteConfigAction with potential RCE payloads
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/SiteConfigAction.action'
        cs-uri-query|contains: 
            - 'Runtime'
            - 'exec'
            - 'getRuntime'
    condition: selection
falsepositives:
    - Legitimate administrative actions (rare)
level: critical

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-51644 Allegra RCE Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/SiteConfigAction.action"; http_uri; content:"Runtime"; http_client_body; content:"exec"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected Allegra instances from the internet.
2. Implement network segmentation to restrict access to the application.
3. Deploy WAF rules to block requests containing OGNL expressions or Java class references.

Long-term Fix:

• Apply vendor patches as soon as they become available.
• Upgrade to a patched version of Allegra.
• Conduct a security audit of the Struts configuration and access controls.

Compensating Controls:

• Enable authentication for all Struts actions.
• Use a reverse proxy to filter malicious payloads.
• Monitor logs for exploitation attempts.

Valters IT
Securing Digital Frontiers