CVE-2026-27844

Executive Summary

CVE-2026-27844 is a low-severity (CVSS 2.7) denial-of-service vulnerability affecting Gallagher Controller 6000 and Controller 7000 diagnostic web interfaces. An authenticated and authorized operator can trigger an uncaught exception (CWE-248) by sending specific crafted requests, causing the controller to restart and resulting in a temporary denial of service. The vulnerability impacts multiple versions of Gallagher Command Centre software. No public exploit code or proof-of-concept is currently available, and the EPSS score is 0.0%, indicating very low exploitation activity in the wild. The vendor has released patches for supported versions.

Supply Chain & Package Security

This vulnerability is not related to any open-source package ecosystem (NPM, PyPI, Go, Ruby). It affects proprietary Gallagher hardware controllers and their associated Command Centre management software. No supply chain implications exist.

CVSS Breakdown & Threat Level

• CVSS Score: 2.7 (Low)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L
• Attack Vector (AV): Network – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low – No special conditions are required for exploitation.
• Privileges Required (PR): High – The attacker must be an authenticated and authorized operator.
• User Interaction (UI): None – No user action is required beyond the attacker's actions.
• Scope (S): Unchanged – The vulnerability does not affect other components.
• Confidentiality (C): None – No data is exposed.
• Integrity (I): None – No data is modified.
• Availability (A): Low – The controller restarts, causing a temporary denial of service.

Threat Level: Low. Exploitation requires authenticated access with operator privileges, limiting the attack surface to internal or trusted users. The impact is a temporary restart, not a persistent outage.

Deep Dive & Mechanics

The vulnerability resides in the diagnostic web interface of Gallagher Controller 6000 and Controller 7000. This interface is used for maintenance and troubleshooting by authorized operators. The flaw is an uncaught exception (CWE-248) that occurs when the web application fails to properly handle specific malformed or unexpected requests.

Root Cause: The diagnostic web interface does not implement proper exception handling for certain input patterns. When an authenticated operator sends a crafted request (e.g., a malformed HTTP parameter, an unexpected data type, or a boundary condition), the application throws an exception that is not caught by any error handler. This unhandled exception propagates up to the controller's main process, causing it to crash and restart.

Attack Flow:

1. Attacker gains authenticated access to the Controller 6000 or 7000 diagnostic web interface (typically on a management network).
2. Attacker sends a specially crafted HTTP request to a vulnerable endpoint (e.g., a diagnostic page or API).
3. The web application processes the request and encounters an unexpected condition (e.g., division by zero, null pointer dereference, or type mismatch).
4. The exception is not caught, causing the web server process to terminate.
5. The controller's watchdog timer detects the process termination and initiates a full controller restart.
6. The controller is unavailable for a short period (typically 1-5 minutes) while it reboots and reinitializes.

Affected Components:

• Controller 6000 (hardware)
• Controller 7000 (hardware)
• Command Centre software versions: 9.50 prior to MR1, 9.40 prior to MR3, 9.30 prior to MR5, 9.20 prior to MR7, and all 9.10 and prior.

Vulnerable vs. Patched Code

Since this is a proprietary hardware/software product, exact code snippets are not publicly available. However, the fix involves adding proper exception handling to the diagnostic web interface.

Vulnerable Code (Conceptual):

# Vulnerable: No exception handling
def handle_diagnostic_request(request):
    data = parse_request(request)
    result = process_data(data)  # May throw unhandled exception
    return generate_response(result)

Patched Code (Conceptual):

# Patched: Exception handling added
def handle_diagnostic_request(request):
    try:
        data = parse_request(request)
        result = process_data(data)
        return generate_response(result)
    except Exception as e:
        log_error(e)
        return generate_error_response("Invalid request")

The patch ensures that any exceptions raised during request processing are caught, logged, and returned as a controlled error response, preventing the controller from crashing.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Authenticated access to the Controller 6000/7000 diagnostic web interface (operator-level credentials).
• Network connectivity to the controller's management IP address (typically on a separate management VLAN).

Exploitation Steps:

1. Identify the target controller's IP address and confirm the diagnostic web interface is accessible (e.g., https://<controller-ip>/diagnostic).
2. Authenticate using valid operator credentials.
3. Send a crafted request to trigger the uncaught exception. Example using curl:

   curl -k -X POST "https://<controller-ip>/diagnostic/api/test" \
        -H "Cookie: session=<valid-session>" \
        -d '{"malformed": "data"}'
   

   (Note: The exact endpoint and payload are not publicly documented; this is a conceptual example.)
4. Monitor the controller's status. If successful, the controller will restart, causing a temporary denial of service.

Alternative Payloads:

• Sending extremely long strings to input fields.
• Sending unexpected data types (e.g., array instead of string).
• Sending requests with missing required parameters.

Blue Team

Detection:

• Monitor for repeated failed authentication attempts followed by successful authentication and unusual API calls.
• Look for HTTP 500 errors or connection resets from the diagnostic web interface.
• Detect controller restarts that occur outside of scheduled maintenance windows.

Prevention:

• Restrict access to the diagnostic web interface to only authorized personnel and management networks.
• Implement network segmentation to isolate controller management interfaces.
• Apply the vendor patch as soon as possible.

Hunting:

• Search logs for patterns of malformed requests to diagnostic endpoints.
• Correlate controller restart events with web interface access logs.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests to /diagnostic/ endpoints with unusual parameters or payloads.
  • Repeated HTTP 500 errors from controller IP addresses.
  • Connection resets or timeouts from controller diagnostic interfaces.

• System IOCs:

  • Unexpected controller restarts (check controller uptime logs).
  • Error logs containing unhandled exception messages (e.g., "Unhandled exception in diagnostic web interface").
  • Watchdog timer events indicating process termination.

• Log IOCs:

  • Command Centre audit logs showing operator access to diagnostic functions followed by controller restarts.
  • Syslog entries from controllers indicating "Controller restart initiated" without a corresponding maintenance event.

Detection Engineering

YARA Rule

rule CVE_2026_27844_Gallagher_DoS {
    meta:
        description = "Detects potential exploitation attempts for CVE-2026-27844 targeting Gallagher Controller diagnostic web interface"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-27844"
        severity = "low"
    strings:
        $s1 = "/diagnostic/" ascii wide nocase
        $s2 = "Unhandled exception" ascii wide nocase
        $s3 = "Controller restart" ascii wide nocase
        $s4 = "500 Internal Server Error" ascii wide nocase
    condition:
        any of ($s1) and any of ($s2, $s3, $s4)
}

Sigma Rule

title: CVE-2026-27844 - Gallagher Controller DoS via Diagnostic Web Interface
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects potential exploitation of CVE-2026-27844 by monitoring for malformed requests to Gallagher Controller diagnostic web interface
author: Valters IT
date: 2026-01-01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-27844
logsource:
    category: webserver
    product: gallagher
detection:
    selection:
        cs-uri-stem:
            - '/diagnostic/*'
        sc-status: 500
    condition: selection
falsepositives:
    - Legitimate diagnostic requests that trigger errors due to network issues
level: low
tags:
    - attack.t1499
    - cve.2026.27844

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2026-27844 - Gallagher Controller DoS via Diagnostic Web Interface";
    flow:to_server,established;
    content:"/diagnostic/"; http_uri;
    http_method;
    content:"POST";
    http_method;
    pcre:"/\/diagnostic\/(api|test|debug)/i";
    classtype:attempted-dos;
    sid:1000001;
    rev:1;
    reference:cve,2026-27844;
    priority:3;
)

Remediation & Mitigation

Immediate Actions:

1. Apply Vendor Patches: Upgrade Command Centre software to the following patched versions:

   • 9.50: Upgrade to vCR9.50.260616a (distributed in 9.50.1587(MR1))
   • 9.40: Upgrade to vCR9.40.260616a (distributed in 9.40.3130(MR3))
   • 9.30: Upgrade to vCR9.30.260616a (distributed in 9.30.3983(MR5))
   • 9.20: Upgrade to vCR9.20.260616a (distributed in 9.20.4349(MR7))
   • 9.10 and prior: Upgrade to a supported version (9.20 or later) and then apply the patch.

2. Network Segmentation: Ensure the diagnostic web interface is only accessible from trusted management networks. Use firewalls to restrict access to authorized IP addresses only.

3. Access Control: Review operator accounts and ensure only necessary personnel have access to the diagnostic interface. Implement multi-factor authentication if supported.

Long-Term Mitigations:

• Implement a web application firewall (WAF) to filter malformed requests to diagnostic endpoints.
• Enable detailed logging and monitoring for the diagnostic web interface.
• Conduct regular security assessments of Gallagher controllers and Command Centre software.
• Establish a patch management process to apply vendor updates promptly.

Workarounds (if patching is not immediately possible):

• Disable the diagnostic web interface if not required for operations.
• Implement strict input validation at the network level (e.g., using a reverse proxy) to block malformed requests.

Valters IT