CVE-2026-40425

Executive Summary

CVE-2026-40425 is a medium-severity authentication-bypass-adjacent vulnerability in the Danelec MacGregor Voyage Data Recorder (VDR) G4e web interface that allows an authenticated administrator to directly edit sensitive authentication-related files, including the root password. The flaw stems from CWE-552 (Files or Directories Accessible to External Parties), where the web interface exposes file-editing functionality beyond its intended scope, enabling an administrator (or an attacker who has compromised an administrator account) to overwrite the root password or other critical authentication data. With a CVSS v3.1 score of 5.7 (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L), the attack requires network reachability to the VDR's web interface and valid low-privilege administrator credentials, but no user interaction. The vulnerability affects marine vessels deploying the MacGregor VDR G4e, a mandatory safety device on commercial ships under SOLAS regulations, meaning unpatched devices pose a direct risk to maritime navigation safety and regulatory compliance.

Technical Analysis

The MacGregor Voyage Data Recorder G4e is a SOLAS-mandated maritime safety device that continuously records sensor data, bridge audio, radar imagery, and voyage parameters. The device exposes a web-based administration interface for configuration, data retrieval, and system monitoring. The vulnerability resides in the file-management capabilities of this web interface, which fails to restrict administrator access to sensitive system files.

The core defect is an authorization boundary failure rooted in CWE-552 — the web application exposes filesystem management functions that permit direct read/write operations on authentication-critical files. Specifically, the administrator account can navigate to and edit files that govern the root account's credentials (e.g., /etc/shadow, /etc/passwd, or an application-specific credential store such as an SQLite database or encrypted properties file used for the VDR's web and OS-level authentication). Because the application treats these files as ordinary configuration data, it does not apply the same privilege separation that would normally prevent a web-application user from modifying OS-level credentials.

From a code perspective, this likely manifests as a directory traversal or unrestricted file-path handling flaw in the web application's file-browsing/editing module. The application validates that a requested file path exists but fails to enforce an allowlist of permitted directories. As a result, a path such as ../../etc/shadow or an absolute path like /etc/shadow resolves to a sensitive file, and the application's save/edit routine writes the attacker-supplied content to that location. Alternatively, the web interface may expose a "system configuration" view that inadvertently maps to the entire root filesystem, with no path sandboxing.

The attack surface is the VDR's HTTP/HTTPS management port (typically port 80 or 443, sometimes 8080 for a secondary admin interface). This web service is reachable from the ship's LAN, and in some configurations from remote shore-side connections via VSAT or other satellite uplinks for fleet management. Because the VDR is a network appliance on a maritime network, it frequently shares the ship's network segment with other systems, increasing the likelihood that a compromised adjacent system could pivot to the VDR's management interface.

The privilege requirement (PR:L) means the attacker must already hold a valid administrator-level login — either through credential theft, default credentials, brute force, or a prior vulnerability. Once authenticated, the attacker's access to the filesystem is essentially unrestricted. The confidentiality, integrity, and availability (C:L/I:L/A:L) impacts are limited in the CVSS model because the attacker must start from an authenticated state; however, the ability to change the root password can result in a complete denial of administrative access for legitimate operators and full system compromise, which the "Low" subscores do not fully communicate.

Exploitation Scenarios

The following attack chain describes how an adversary exploits CVE-2026-40425 in practice:

Step 1 — Reconnaissance and Target Identification. The attacker scans for vulnerable VDRs using Shodan or Censys with queries such as http.title:"MacGregor VDR" or product:"MacGregor Voyage Data Recorder". Alternatively, the attacker gains foothold on the ship's LAN through a previously compromised crew laptop, a vulnerable passenger Wi-Fi captive portal, or a spear-phishing campaign targeting ship officers. The VDR's web interface is typically identified by scanning for default ports (80/443/8080) and banner grabbing.

Step 2 — Authentication. The attacker attempts to log in to the web interface. Many maritime devices ship with default credentials (e.g., admin/admin or root/password). If defaults are unchanged, the attacker gains immediate administrator access. If not, they may use credential-stuffing or brute-force (the interface may have weak rate limiting). Alternatively, credentials may be harvested from a prior phishing campaign targeting the crew's email accounts, since maritime crews frequently reuse passwords.

Step 3 — Triggering the Flaw. Once authenticated as an administrator, the attacker navigates to the web interface's file management or system configuration module. The attacker uses the file-browsing feature to traverse to the authentication store. For example, they navigate to ../../etc/shadow or access the file directly via a URL parameter such as http://[VDR_IP]/admin/file?path=../../../etc/shadow. If the interface uses an "Edit" function, they open the file in the web-based editor.

Step 4 — Payload/Execution. The attacker edits the root password hash within the shadow file (or equivalent credential store), replacing the existing hash with one generated for a password of their choosing (e.g., using openssl passwd -6 to generate a SHA-512 hash). They save the file. Because the application performs no path sandboxing or privilege-dropping, the write operation succeeds with root privileges.

Step 5 — Post-Exploitation. The attacker now holds the VDR's root password. They SSH or telnet into the device as root, gaining full OS-level shell access. From the VDR, they can:

• Exfiltrate recorded voyage data (including sensitive navigation logs, bridge audio, and radar data) to a remote server.
• Disable the VDR's recording function entirely, violating SOLAS compliance and potentially facilitating maritime insurance fraud.
• Modify sensor data or timestamps — inserting false records to cover illegal activities (e.g., illegal fishing, pollution, entering restricted waters).
• Use the VDR as a pivot point to reach other shipboard networks (navigation, engine control, security systems).
• Persist for future operations by installing a backdoor or creating an additional administrator account.

Impact Pairing with Other Vulnerabilities. If the attacker already has low-privilege access (e.g., a "guest" or "monitoring" account), the flaw's privilege requirement (PR:L) is met, and the attack proceeds as above. In cases where multiple VDRs in a fleet share identical default credentials, a single compromised vessel's credentials can be tested across the entire fleet.

Impact Assessment

Business Impact. The MacGregor VDR G4e is a SOLAS-mandated safety recorder on commercial vessels. Unauthorized modification of its authentication infrastructure enables an attacker to lock out legitimate operators (denial of service against safety systems), falsify voyage records (legal and insurance liability), or leak confidential voyage data (competitive intelligence for shipping companies, pirates, or state adversaries). For shipping lines operating fleets of SOLAS-compliant vessels, a single compromised VDR can trigger regulatory inspection failures, port-state control detention, and reputational damage.

Affected Systems. VDR G4e devices running firmware versions prior to V5.250. This includes units deployed on bulk carriers, container ships, LNG carriers, tankers, and offshore support vessels. Because the VDR is physically hardened and seaworthy, firmware updates require either an onboard engineer with the patch file or a service technician attendance — the vendor itself acknowledges the patch "may be applied at the earliest service attendance rather than waiting for an annual performance test."

Blast Radius. The CVSS vector (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L) indicates a low direct impact per subscore, but the composite attack scenario — gaining root on a safety-critical maritime device — is more severe than the score suggests. A root shell on the VDR opens a lateral movement path to the ship's entire network. The VDR is typically connected to the ship's Ethernet backbone, alongside the ECDIS, engine monitoring, AIS, and fleet management systems. Compromise of the VDR admin account can therefore cascade to a full shipboard network takeover.

Exploit Economics. With a CVSS of 5.7, this is not a land-and-expand target for mass cybercrime. However, for nation-state adversaries targeting maritime infrastructure (e.g., to track military logistics, disrupt energy shipping, or conduct sabotage), the VDR is a highly valuable reconnaissance and disruption node. EPSS score of 0.00376 (30.3rd percentile) indicates this flaw is not currently being actively exploited; however, the low EPSS reflects lack of public PoC rather than absence of threat actor interest, particularly in state-sponsored maritime intrusion campaigns.

Detection Guidance

Sigma Rule

title: MacGregor VDR G4e - Unauthorized Authentication File Modification
id: 9d7a3f1b-2c4e-4d5f-8a6b-3e2c1d0f9a8b
status: experimental
description: Detects successful modification of sensitive authentication files via the MacGregor Voyage Data Recorder G4e web interface (CVE-2026-40425).
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-40425
author: Valtersit Threat Intelligence
date: 2026/06/17
logsource:
    product: linux
    category: file_event
detection:
    selection_auth_files:
        TargetFilename|contains:
            - '/etc/shadow'
            - '/etc/passwd'
            - '/etc/security/'
            - '/var/lib/vdr/'
    selection_source:
        Image|contains:
            - '/usr/sbin/httpd'
            - '/usr/local/vdr/'
            - 'nginx'
            - 'apache'
    condition: selection_auth_files and selection_source
level: high
falsepositives:
    - Legitimate system administration via console or SSH (exclude if only web-interface processes are present)
    - Manufacturer service activities during firmware upgrade
fields:
    - TargetFilename
    - Image
    - SourceAddress
    - User

YARA Rule

rule macgregor_vdr_auth_file_edit {
    meta:
        author = "Valtersit Threat Intelligence"
        date = "2026-06-17"
        version = "1.0"
        description = "Detects suspicious HTTP requests targeting authentication file paths in MacGregor VDR G4e web interface"
        reference = "CVE-2026-40425"
    strings:
        $s1 = "/etc/shadow" ascii wide
        $s2 = "/etc/passwd" ascii wide
        $s3 = "file?path=" ascii wide
        $s4 = "edit?file=" ascii wide
        $s5 = "SaveConfiguration" ascii wide
        $s6 = "/admin/file" ascii wide
        $s7 = "chpasswd" ascii wide
        $s8 = "root:" ascii wide
        $s9 = "../../" ascii wide
    condition:
        uint16(0) == 0x4854 and // "HT" (HTTP)
        any of ($s1, $s2) and
        2 of ($s3, $s4, $s5, $s6, $s7, $s8, $s9)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-40425 - MacGregor VDR G4e Authentication File Access";
    flow:established,to_server;
    content:"/etc/shadow"; http_uri; nocase;
    content:"/etc/passwd"; http_uri; nocase;
    content:"file"; http_uri; nocase;
    content:"edit"; http_uri; nocase;
    pcre:"/(\/etc\/(shadow|passwd)|\.\.\/\.\.\/)/i";
    sid:4042501; rev:1; priority:1;
    reference:cve,CVE-2026-40425;
    metadata:attack_target VDR, deployment maritime, tag CVE-2026-40425;
)

alert http any any -> any any (msg:"CVE-2026-40425 - MacGregor VDR G4e Path Traversal Attempt";
    flow:established,to_server;
    content:"GET"; http_method;
    pcre:"/(\.\.\/)+/i";
    http_uri;
    sid:4042502; rev:1; priority:1;
    reference:cve,CVE-2026-40425;
)

Elastic Detection

/** EQL rule to detect suspicious file edits via MacGregor VDR web interface */
any where
  process.name in ("httpd", "nginx", "apache2", "vdr-web") and
  process.args like "*file*" and
  (
    process.args like "*/etc/shadow" or
    process.args like "*/etc/passwd" or
    process.args like "*shadow*" or
    process.args like "*password*"
  ) and
  not process.args like "*backup*"

Splunk SPL Query

index=* sourcetype="linux:audit" OR sourcetype="linux:syslog"
| search (path="/etc/shadow" OR path="/etc/passwd" OR file="shadow" OR file="passwd")
    AND (process="*httpd*" OR process="*nginx*" OR process="*apache*" OR process="*java*")
| stats count by host, src_ip, user, process, path
| where count > 0
| eval severity = case(count > 5, "CRITICAL", count > 1, "HIGH", true(), "MEDIUM")
| table _time, host, src_ip, user, process, path, count, severity
| sort - _time

Wazuh OSSEC Rule

<group name="syscheck,attacks,">
    <rule id="404250" level="12">
        <if_sid>550</if_sid>
        <field name="file">/etc/shadow|/etc/passwd|/etc/security</field>
        <description>MacGregor VDR G4e: Sensitive authentication file modified via web interface (CVE-2026-40425)</description>
        <group>macgregor_vdr,cve-2026-40425</group>
    </rule>
    <rule id="404251" level="10">
        <if_sid>550</if_sid>
        <field name="process">httpd|nginx|apache</field>
        <field name="file">\.\./</field>
        <description>MacGregor VDR G4e: Path traversal attempt via web admin (CVE-2026-40425)</description>
        <group>macgregor_vdr,cve-2026-40425</group>
    </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED — single source claims patch (not independently confirmed)).

1. Immediate Mitigations (Until Patch Applied):

• Restrict network access: Implement firewall rules to limit access to the VDR web interface (ports 80, 443, 8080) to only the ship's bridge workstations or the authorized fleet management shore-side IP ranges. Block access from passenger Wi-Fi networks and any general crew LAN segments.
• Change all default credentials: Immediately change the default administrator passwords on all VDR G4e units. Use strong, unique passwords per device. Ensure the web interface admin password differs from the OS-level root password.
• Disable remote management: If the VDR is accessible via VSAT or other satellite uplinks for shore-side fleet monitoring, consider disabling remote access or enforcing a strict VPN-based tunnel that requires multi-factor authentication before reaching the management interface.
• Monitor access logs: Enable and review audit logs for the web interface. Look for repeated login failures, login from unusual IPs, and any file-editing activity.
• Isolate the VDR network segment: Segment the ship's network so the VDR is on a dedicated management VLAN, physically or logically separated from crew internet access, passenger Wi-Fi, and other non-critical systems.

2. Patch/Upgrade Steps:

• Obtain the firmware: Contact Danelec support (https://www.danelec.com/contact) to obtain firmware version V5.250. The vendor states this version resolves the vulnerability.
• Schedule update: Install the firmware at the next service attendance. If feasible, expedite a service visit rather than waiting for the annual performance test, given the severity of a root-password takeover.
• Apply via engineering console: Follow Danelec's documented firmware upgrade procedure. Typically this involves connecting a laptop directly to the VDR's maintenance port and running the update utility. Ensure the ship's engineer or authorized service technician performs the upgrade.
• Post-update verification: After applying V5.250, verify the firmware version is displayed correctly in the web interface, and confirm that file-editing functions no longer permit access to /etc/shadow or equivalent sensitive files. Re-test by attempting to navigate to a sensitive path and confirming access denial.

3. Long-Term Hardening:

• Implement a maritime cybersecurity program: Adopt IMO MSC.428(98) guidelines for cyber risk management on board vessels. This includes regular vulnerability scanning of shipboard IT/OT equipment (including VDRs), patch management, and incident response procedures specific to maritime networks.
• Inventory and baseline: Maintain an up-to-date inventory of all VDR units, their firmware versions, and their network exposure. Establish a maintenance window for applying firmware updates to all safety-critical devices.
• Network segmentation architecture: Design shipboard networks with the VDR and other safety systems (ECDIS, GMDSS) on a dedicated OT segment with strict access control lists. Do not allow direct internet routing to these devices; place them behind a maritime security gateway/NGFW.
• Credential rotation policy: Enforce periodic rotation of all device credentials (web admin, OS root, SNMP community strings) at a minimum interval of 90 days. Store credentials in a secure password manager accessible only to the bridge officers and fleet IT staff.
• Honeypot monitoring: Deploy network-level detection (IDS/IPS) on the ship's backbone, using the Suricata rules above, to detect path traversal attempts or authentication file editing targeting VDRs and similar systems.
• Fleet-wide vulnerability management: Ensure the vendor's patch confidence is upgraded by requesting confirmation in writing from Danelec that V5.250 fully remediates CWE-552 in all configurations. If independent verification is not obtained, consider additional compensating controls (e.g., a reverse-proxy WAF in front of the VDR that blocks path traversal and file-edit endpoints).

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2026-40425
2. Danelec Contact / Advisory: https://www.danelec.com/contact
3. ICS-CERT (CNA) Advisory: https://www.cisa.gov/news-events/ics-advisories/icsa-26-XXX-XX (reference ID per CNA publication)
4. CWE-552 Details: https://cwe.mitre.org/data/definitions/552.html
5. EPSS Information: https://www.first.org/epss/

Threat Actor Activity: As of the date of this report, there is no evidence of active exploitation in the wild, and no public exploit code exists. The CVE is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. However, state-sponsored maritime-focused threat actors (e.g., groups assessed as operating in the Baltic and Black Sea regions) have historically targeted shipboard navigation and recording systems. The ESPS score of 0.00376 (30.3rd percentile) indicates that exploitation likelihood is currently low but expected to rise as the maritime security community disseminates this advisory and as VDRs become more network-exposed through digitalized fleet management systems.