CVE-2026-27553: Password Hash Disclosure Vulnerability

CVE-2026-27553 Overview

CVE-2026-27553 is an authenticated information disclosure vulnerability affecting a web management interface that exposes the /index.php/diagnostics_tab/ajax_diag_table_rows endpoint. A low-privileged remote attacker holding a valid user cookie can manipulate the schema path parameter to retrieve all user password hashes stored by the application. The weakness is classified under CWE-497: Exposure of Sensitive System Information to an Unauthorized Control Sphere. The advisories were published by CERT-VDE, indicating the affected component is used in industrial or operational technology environments.

Critical Impact
Any authenticated user, regardless of role, can extract every stored password hash, enabling offline cracking and downstream account takeover of higher-privileged accounts.

Affected Products

Product details are enumerated in CERT-VDE advisories VDE-2026-014, VDE-2026-027, and VDE-2026-028
Web management interface exposing /index.php/diagnostics_tab/ajax_diag_table_rows
Vendor and model list: refer to the CERT-VDE Advisory VDE-2026-014

Discovery Timeline

2026-09-16 - CVE-2026-27553 published to the National Vulnerability Database
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-27553

Vulnerability Analysis

The vulnerable endpoint /index.php/diagnostics_tab/ajax_diag_table_rows accepts a schema path parameter that controls which database table or schema is queried for display in a diagnostics view. The endpoint fails to enforce authorization checks tied to the requested schema, treating any authenticated cookie as sufficient permission to read arbitrary tables. When an attacker substitutes the path with a reference to the user or credential table, the endpoint returns password hash fields in its JSON response. The disclosure includes hashes belonging to administrative accounts, which extends the impact well beyond the attacker's original privilege level.

Root Cause

The root cause is missing access control on a diagnostic function that was designed for privileged operators but is reachable by any authenticated session [CWE-497]. Server-side logic trusts the client-supplied schema identifier without validating that the caller is entitled to read the referenced data.

Attack Vector

Exploitation requires network reachability to the management interface and a valid low-privileged user cookie. The attacker issues a crafted HTTP request to the diagnostics AJAX endpoint with a schema path parameter pointing to the user credentials table. The server responds with the table rows, including password hash columns. No user interaction is required beyond the attacker's authenticated session, and no memory corruption or code execution primitive is needed. Details on the exact parameter grammar are available in the CERT-VDE advisories linked above.

Detection Methods for CVE-2026-27553

Indicators of Compromise

HTTP requests to /index.php/diagnostics_tab/ajax_diag_table_rows from user accounts that do not normally access diagnostic pages
Diagnostic endpoint requests containing schema or table parameters referencing user, account, or credential tables
Unusually large JSON responses from the diagnostics endpoint compared to baseline request patterns

Detection Strategies

Instrument the web application to log the full query string and requesting user role for every call to the diagnostics AJAX endpoints
Alert on response payloads from ajax_diag_table_rows that contain hash-formatted strings such as $2y$, $argon2, or fixed-length hex digests
Correlate low-privileged session identifiers with access to administrative diagnostic routes

Monitoring Recommendations

Forward web server and application logs from the management interface to a centralized analytics platform for retention and query
Baseline normal usage of the diagnostics tab per user role and flag deviations
Monitor for post-exploitation password spraying or credential stuffing against the same or related systems following diagnostic endpoint access

How to Mitigate CVE-2026-27553

Immediate Actions Required

Restrict network access to the management interface using firewall rules or a management VLAN so only trusted operator workstations can reach it
Rotate all local account passwords on affected devices, prioritizing administrative accounts whose hashes may have been exposed
Audit the application's authentication logs for use of the diagnostics endpoint by non-administrative users

Patch Information

Refer to the vendor-specific fixed versions listed in CERT-VDE Advisory VDE-2026-014, CERT-VDE Advisory VDE-2026-027, and CERT-VDE Advisory VDE-2026-028. Apply the firmware or software updates identified for your specific product model as soon as the vendor's change control process permits.

Workarounds

Disable the diagnostics tab or the ajax_diag_table_rows route in the web server configuration if the diagnostic feature is not required for operations
Limit account provisioning on the management interface to a minimum set of trusted users until patches are applied
Place the management interface behind a reverse proxy that enforces IP allowlisting and additional authentication

bash

# Example nginx allowlist restricting the diagnostics endpoint to operator subnet
location ~ ^/index\.php/diagnostics_tab/ {
    allow 10.10.20.0/24;
    deny all;
    proxy_pass http://backend;
}