CVE-2026-13527: Class Timetabling System SQLi Vulnerability

CVE-2026-13527 Overview

CVE-2026-13527 is a SQL injection vulnerability in SourceCodester Class and Exam Timetabling System 1.0. The flaw resides in the /preview4.php script, where the course_year_section parameter is passed to a backend SQL query without proper sanitization. Remote attackers can inject arbitrary SQL statements over the network without authentication or user interaction. Public disclosure of the exploit details means opportunistic attackers can weaponize the issue against exposed installations. The vulnerability is categorized under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component.

Critical Impact
Unauthenticated remote attackers can manipulate database queries through the course_year_section parameter, potentially exposing student, course, and scheduling records stored by the application.

Affected Products

SourceCodester Class and Exam Timetabling System 1.0
/preview4.php endpoint processing the course_year_section argument
Deployments exposing the PHP application to untrusted networks

Discovery Timeline

2026-06-29 - CVE-2026-13527 published to NVD
2026-06-29 - Last updated in NVD database

Technical Details for CVE-2026-13527

Vulnerability Analysis

The vulnerability exists in the preview4.php handler of the Class and Exam Timetabling System. The application accepts the course_year_section argument from the client and concatenates it directly into a SQL statement executed against the backend database. Because the input is neither validated nor parameterized, attackers can break out of the intended query context and append arbitrary SQL clauses.

Exploitation requires no credentials and no user interaction. The attacker only needs network reachability to the vulnerable PHP endpoint. Successful injection allows attackers to enumerate database schemas, extract records, or manipulate stored data depending on the privileges of the database user configured for the application.

The EPSS probability is 0.263% as of 2026-07-02, indicating low but non-zero prediction of near-term exploitation. However, because the vulnerability details and reproduction steps are already public on VulDB and GitHub, defenders should treat exposed instances as high risk.

Root Cause

The root cause is missing input neutralization on the course_year_section parameter before it is used in a dynamic SQL query. The application relies on direct string concatenation rather than prepared statements with bound parameters, violating standard secure coding practices for PHP database access.

Attack Vector

The attack vector is network-based. An attacker sends a crafted HTTP request to /preview4.php with a malicious course_year_section value containing SQL metacharacters and injected clauses. The backend interprets the payload as part of the intended SQL statement and executes it, returning data or triggering side effects visible to the attacker.

Technical reproduction details are available in the GitHub Issue Tracker and the VulDB CVE Details entry. No verified proof-of-concept code is reproduced here.

Detection Methods for CVE-2026-13527

Indicators of Compromise

HTTP requests to /preview4.php containing SQL metacharacters such as ', --, UNION, or SLEEP( in the course_year_section parameter
Unusual database error responses returned to clients from the timetabling application
Unexpected outbound queries or large result sets from the application's database user account

Detection Strategies

Inspect web server access logs for anomalous query strings targeting preview4.php, particularly encoded SQL syntax in course_year_section
Deploy web application firewall (WAF) rules to flag classic SQL injection patterns against the timetabling application URIs
Enable database query logging and alert on queries referencing the course_year_section value that contain tautologies, unions, or stacked statements

Monitoring Recommendations

Baseline normal query volumes from the application's database account and alert on deviations
Monitor for authentication or schema enumeration queries (information_schema, mysql.user) originating from the web tier
Forward web and database logs into a centralized analytics platform for cross-source correlation of injection attempts

How to Mitigate CVE-2026-13527

Immediate Actions Required

Restrict network exposure of the Class and Exam Timetabling System to trusted internal networks or VPN users until a fix is applied
Place a WAF or reverse proxy with SQL injection signatures in front of the application
Audit the database user configured for the application and revoke unnecessary privileges such as FILE, DROP, or cross-database access

Patch Information

At the time of publication, no vendor patch is listed in the NVD entry for CVE-2026-13527. Administrators should monitor the SourceCodester website and the VulDB Vulnerability Info page for updated remediation guidance. Where source code access is available, developers should replace string concatenation in preview4.php with parameterized queries using PDO or MySQLi prepared statements.

Workarounds

Apply server-side allowlist validation on the course_year_section parameter, permitting only expected character classes
Introduce input length limits and reject requests containing SQL metacharacters at the application gateway
Disable the /preview4.php endpoint if it is not required for production operations

bash

# Example nginx location block to block obvious SQLi patterns against preview4.php
location = /preview4.php {
    if ($args ~* "(union|select|sleep\(|--|';|/\*)") {
        return 403;
    }
    include fastcgi_params;
    fastcgi_pass unix:/run/php/php-fpm.sock;
}