CVE-2026-30574: Pharmacy Management System Auth Bypass

CVE-2026-30574 Overview

A Business Logic vulnerability exists in SourceCodester Pharmacy Product Management System 1.0 in the add-sales.php file. The application fails to verify if the requested sales quantity (txtqty) exceeds the available stock level. An attacker can manipulate the request to purchase a quantity that is significantly higher than the actual available stock, potentially leading to inventory management failures, financial discrepancies, and data integrity issues.

Critical Impact

This vulnerability allows attackers to bypass inventory validation controls, enabling overselling of pharmaceutical products beyond available stock levels, which could result in significant business disruption and financial losses.

Affected Products

• Senior-walter Web-based Pharmacy Product Management System 1.0
• SourceCodester Pharmacy Product Management System 1.0

Discovery Timeline

• 2026-03-27 - CVE CVE-2026-30574 published to NVD
• 2026-03-31 - Last updated in NVD database

Technical Details for CVE-2026-30574

Vulnerability Analysis

The vulnerability resides in the sales processing functionality within add-sales.php. When a user submits a sales transaction, the application accepts the quantity value (txtqty) from the client-side request without performing server-side validation against the current stock inventory. This creates a business logic flaw where the system processes sales orders regardless of whether sufficient stock exists to fulfill them.

The lack of proper validation allows malicious actors to craft requests with inflated quantity values, bypassing the intended business rules that should prevent overselling. This type of vulnerability is classified under CWE-841 (Improper Enforcement of Behavioral Workflow), which highlights the failure to properly enforce the expected sequence and rules of a business process.

Root Cause

The root cause of this vulnerability is the absence of server-side stock level validation in the add-sales.php file. The application trusts the client-supplied txtqty parameter without cross-referencing it against the actual available inventory in the database. Proper business logic should include a check to ensure that txtqty does not exceed the current stock quantity before processing the sale. The missing validation allows the application to record sales transactions that exceed physical inventory limits.

Attack Vector

The attack is network-accessible and requires no authentication or user interaction to exploit. An attacker can intercept or directly craft HTTP requests to the add-sales.php endpoint, manipulating the txtqty parameter to specify quantities far exceeding available stock. The attack flow involves:

1. Identifying a product with limited stock in the pharmacy system
2. Submitting a sales request with an artificially inflated quantity value
3. The server processes the request without validating against available stock
4. The system records the oversale, creating inventory discrepancies

Technical details and proof-of-concept information can be found in the GitHub PoC Repository.

Detection Methods for CVE-2026-30574

Indicators of Compromise

• Sales records showing quantities sold exceeding previous stock levels for specific products
• Negative inventory values in the database indicating overselling has occurred
• Unusual HTTP POST requests to add-sales.php with abnormally high txtqty values
• Discrepancies between physical inventory counts and system-recorded stock levels

Detection Strategies

• Implement application-level logging to capture all sales transactions including quantity requested vs. available stock
• Monitor web application firewall (WAF) logs for repeated requests with unusually large quantity parameters
• Deploy anomaly detection rules to identify sales transactions that result in negative inventory states
• Conduct regular database integrity checks comparing sales volumes against inventory movements

Monitoring Recommendations

• Set up alerts for any inventory values dropping below zero in the database
• Monitor add-sales.php endpoint for high-frequency requests or requests with outlier quantity values
• Implement real-time dashboard monitoring for sales-to-stock ratio anomalies
• Enable detailed transaction logging with before/after stock levels for audit purposes

How to Mitigate CVE-2026-30574

Immediate Actions Required

• Disable or restrict access to the add-sales.php functionality until a proper fix is implemented
• Implement network-level access controls to limit who can access the sales processing endpoints
• Review existing sales records for evidence of exploitation and correct any inventory discrepancies
• Add temporary manual approval workflows for large quantity sales transactions

Patch Information

No official vendor patch is currently available for this vulnerability. Organizations using SourceCodester Pharmacy Product Management System 1.0 should implement the workarounds listed below or consider migrating to a more actively maintained pharmacy management solution. Monitor the vendor resources and security advisories for future patch releases.

Workarounds

• Implement server-side validation in add-sales.php to check that txtqty does not exceed current stock levels before processing
• Add database-level constraints or triggers to prevent stock values from becoming negative
• Deploy a web application firewall (WAF) with custom rules to block requests with abnormally high quantity values
• Implement rate limiting on the sales endpoint to reduce the impact of automated exploitation attempts
• Add input validation to ensure txtqty is a positive integer within reasonable bounds

// Example validation logic to add in add-sales.php
// Check available stock before processing sale
$product_id = $_POST['product_id'];
$requested_qty = (int)$_POST['txtqty'];

// Query current stock level
$stock_query = "SELECT quantity FROM products WHERE id = ?";
$stmt = $conn->prepare($stock_query);
$stmt->bind_param("i", $product_id);
$stmt->execute();
$result = $stmt->get_result();
$product = $result->fetch_assoc();

// Validate requested quantity against available stock
if ($requested_qty > $product['quantity']) {
    die("Error: Requested quantity exceeds available stock.");
}
// Proceed with sale processing only if validation passes