CVE-2026-15559: Online Leave Management System SQLi Flaw

CVE-2026-15559 Overview

CVE-2026-15559 is a SQL injection vulnerability in CodeAstro Simple Online Leave Management System 1.0. The flaw resides in the /SimpleOnlineLeave/admin/accept.php endpoint, specifically within the POST handler that processes the appid parameter. An authenticated attacker can manipulate the appid argument to inject arbitrary SQL statements against the backend database. The vulnerability is remotely exploitable and requires only low privileges. Public exploit details are available, increasing the likelihood of opportunistic abuse against exposed installations. The issue is classified under CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component.

Critical Impact
Remote SQL injection through the appid parameter allows attackers to read, modify, or delete data in the leave management database.

Affected Products

CodeAstro Simple Online Leave Management System 1.0
Component: /SimpleOnlineLeave/admin/accept.php POST handler
Vulnerable parameter: appid

Discovery Timeline

2026-07-13 - CVE-2026-15559 published to the National Vulnerability Database (NVD)
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-15559

Vulnerability Analysis

The vulnerability exists in the administrative accept handler of the Simple Online Leave Management System. The accept.php script receives an appid value through an HTTP POST request and passes it into a SQL query without proper sanitization or parameterization. Because the parameter is concatenated directly into the query string, an attacker can break out of the intended SQL context and append arbitrary clauses. Successful exploitation exposes the application database to unauthorized read and write operations, including modification of leave request records and potential extraction of user credentials stored by the application.

Root Cause

The root cause is improper neutralization of special elements passed through the appid POST parameter, categorized as CWE-74. The application constructs SQL statements through string concatenation rather than using prepared statements or bound parameters. As a result, single quotes, comment sequences, and SQL keywords supplied by the client are interpreted as query syntax by the database engine.

Attack Vector

Exploitation requires network access to the administrative interface and a low-privilege authenticated session, since the vulnerable endpoint lives under /admin/. An attacker submits a crafted POST request to /SimpleOnlineLeave/admin/accept.php with a malicious appid value containing SQL metacharacters. Payloads typically use boolean-based, union-based, or time-based techniques to enumerate database schema, extract data, or alter records. Public disclosure through the GitHub issue report and VulDB entry for CVE-2026-15559 lowers the barrier for reproduction.

Detection Methods for CVE-2026-15559

Indicators of Compromise

POST requests to /SimpleOnlineLeave/admin/accept.php containing SQL metacharacters such as ', --, UNION, SLEEP(, or OR 1=1 in the appid parameter
Unexpected HTTP 500 responses or elevated response latency from accept.php correlating with unusual appid values
Web server access logs showing repeated POSTs to accept.php from a single source with varying appid payload lengths

Detection Strategies

Deploy web application firewall (WAF) signatures that inspect POST bodies for SQL injection patterns targeting the appid parameter
Enable database query logging and alert on parameterized queries containing suspicious tautologies or stacked statements originating from the leave management application user
Correlate authentication events for low-privilege admin accounts with subsequent bursts of requests to accept.php for anomaly identification

Monitoring Recommendations

Forward web server, application, and database logs to a centralized analytics platform for cross-source correlation
Baseline normal request rates and payload sizes for /SimpleOnlineLeave/admin/ endpoints and alert on deviations
Monitor outbound network connections from the database host for signs of exfiltration following suspicious query activity

How to Mitigate CVE-2026-15559

Immediate Actions Required

Restrict network access to /SimpleOnlineLeave/admin/ to trusted IP ranges or place it behind a VPN
Rotate credentials for all administrative accounts used with the Simple Online Leave Management System
Review database audit logs for evidence of unauthorized queries against tables referenced by accept.php

Patch Information

At the time of publication, no vendor patch has been referenced in the NVD or VulDB advisory for CVE-2026-15559. Operators should contact CodeAstro for an updated release or apply source-level fixes that replace concatenated SQL with prepared statements using bound parameters for the appid value.

Workarounds

Apply a WAF rule that blocks POST requests to /SimpleOnlineLeave/admin/accept.php when the appid parameter is not strictly numeric
Add server-side input validation in accept.php that casts appid to an integer before use in any SQL statement
Enforce least-privilege database accounts so the application user cannot execute DROP, ALTER, or cross-database SELECT statements

bash

# Example ModSecurity rule to enforce numeric appid on the vulnerable endpoint
SecRule REQUEST_URI "@streq /SimpleOnlineLeave/admin/accept.php" \
    "chain,phase:2,deny,status:403,id:1015559,msg:'CVE-2026-15559 appid validation'"
    SecRule ARGS:appid "!@rx ^[0-9]+$" "t:none"