CVE-2026-90518: PHPGurukul Bank Locker Auth Bypass Flaw

CVE-2026-90518 Overview

CVE-2026-90518 is an improper access control vulnerability in PHPGurukul Bank Locker Management System 1.0. The flaw resides in the sidebar.php file, where manipulation of the UserType argument allows an attacker to bypass role-based access restrictions. The issue is classified under CWE-266: Incorrect Privilege Assignment.

A remote attacker with low privileges can exploit the weakness over the network without user interaction. Public exploit details have been released, increasing the likelihood of opportunistic abuse against exposed instances.

Critical Impact
An authenticated low-privileged user can manipulate the UserType parameter processed by sidebar.php to gain access to functionality intended for higher-privileged roles.

Affected Products

PHPGurukul Bank Locker Management System 1.0
Component: sidebar.php
Deployments exposing the application to untrusted networks

Discovery Timeline

2026-09-13 - CVE-2026-90518 published to NVD
2026-09-14 - Last updated in NVD database

Technical Details for CVE-2026-90518

Vulnerability Analysis

The vulnerability is an improper access control issue affecting the sidebar.php component of PHPGurukul Bank Locker Management System 1.0. The application relies on the client-supplied UserType value to determine which menu items and administrative options render for the current session. Because the server trusts this parameter without re-validating the user's actual role against server-side session data, an attacker can escalate visibility and access to functions reserved for privileged accounts.

The weakness maps to CWE-266: Incorrect Privilege Assignment. It affects confidentiality, integrity, and availability at a limited level, since the exposed functions still require the attacker to hold a valid low-privileged session.

Root Cause

The root cause is reliance on a client-controllable UserType value for access control decisions inside sidebar.php. The application does not enforce authoritative role checks server-side before exposing higher-privileged menu entries and their linked handlers.

Attack Vector

Exploitation is remote and network-based. An attacker authenticates with any low-privileged account, then modifies the UserType parameter transmitted to sidebar.php to impersonate a higher role. Public disclosure details are available in the GitHub Issue Discussion and the VulDB entry for CVE-2026-90518.

No verified proof-of-concept code is reproduced here. Refer to the referenced advisories for technical details.

Detection Methods for CVE-2026-90518

Indicators of Compromise

HTTP requests to sidebar.php containing manipulated or unexpected UserType values inconsistent with the authenticated session's role.
Session activity where a single user account accesses administrative pages or actions typically restricted to higher-privileged roles.
Sudden appearance of privileged menu navigations from accounts historically limited to user-level operations.

Detection Strategies

Enable verbose access logging on the web server and correlate the UserType parameter value with the authenticated role stored server-side.
Deploy a web application firewall rule that flags mismatches between session role and submitted UserType values.
Review application audit trails for privilege changes or administrative actions performed by accounts that lack the corresponding role.

Monitoring Recommendations

Alert on any request to sidebar.php where the UserType query or POST parameter is present and modifiable by the client.
Baseline normal user navigation patterns and flag deviations toward administrative endpoints.
Forward web server and PHP application logs to a centralized SIEM or data lake for long-term correlation and hunting.

How to Mitigate CVE-2026-90518

Immediate Actions Required

Restrict network exposure of PHPGurukul Bank Locker Management System 1.0 to trusted networks or VPN-only access until a vendor fix is available.
Audit existing accounts and revoke unnecessary privileges to reduce blast radius of any privilege escalation.
Review recent access logs for suspicious UserType manipulation against sidebar.php.

Patch Information

No official vendor patch is referenced in the current NVD entry. Administrators should monitor the PHP Gurukul website and the VulDB advisory for updates. Until a patch is released, apply the compensating controls listed below.

Workarounds

Modify sidebar.php to derive the effective role exclusively from a server-side session variable rather than the request-supplied UserType parameter.
Introduce a centralized authorization check that validates the session role before rendering privileged menu items or handling their actions.
Place the application behind a web application firewall configured to strip or normalize the UserType parameter on inbound requests.
Enforce strong authentication and account lockout policies to limit an attacker's ability to obtain the low-privileged foothold required for exploitation.

bash

# Example WAF rule concept (ModSecurity) - strip client-supplied UserType
SecRule ARGS_NAMES "@streq UserType" \
    "id:1090518,phase:2,deny,status:403,log,msg:'Blocked client-supplied UserType parameter (CVE-2026-90518)'"