CVE-2026-30573: Pharmacy Management System Logic Flaw

CVE-2026-30573 Overview

A Business Logic vulnerability exists in SourceCodester Pharmacy Product Management System 1.0. The vulnerability is located in the add-sales.php file where the application fails to validate the txtprice and txttotalcost parameters, allowing attackers to submit negative values for sales transactions. This leads to incorrect financial calculations, corruption of sales reports, and potential financial loss.

Critical Impact

Attackers can manipulate sales transactions by submitting negative price values, leading to corrupted financial records, fraudulent credits, and potential monetary losses for organizations using this pharmacy management system.

Affected Products

• SourceCodester Pharmacy Product Management System 1.0
• add-sales.php component

Discovery Timeline

• 2026-04-01 - CVE CVE-2026-30573 published to NVD
• 2026-04-01 - Last updated in NVD database

Technical Details for CVE-2026-30573

Vulnerability Analysis

This vulnerability stems from insufficient input validation in the sales transaction processing workflow. The add-sales.php file accepts user-supplied values for pricing parameters without implementing proper server-side validation or business logic constraints. By exploiting this flaw, an attacker with access to the sales interface can submit transactions with negative monetary values, effectively creating fraudulent credits or reversing legitimate sales totals.

The vulnerability is classified under CWE-1284 (Improper Validation of Specified Quantity in Input), which describes scenarios where applications fail to ensure that numeric inputs fall within expected and valid ranges. In a pharmacy management context, allowing negative prices violates fundamental business logic rules that should prevent such anomalous data from being processed.

Root Cause

The root cause of this vulnerability is the absence of server-side validation for the txtprice and txttotalcost form parameters in the add-sales.php file. The application directly processes user-supplied values without checking whether they meet expected business constraints (i.e., non-negative monetary values). This oversight allows attackers to bypass any client-side validation that may exist and submit malformed transaction data directly to the server.

Attack Vector

The attack can be executed remotely over the network without requiring authentication. An attacker can intercept or craft HTTP POST requests to the add-sales.php endpoint, modifying the txtprice or txttotalcost parameters to include negative values. This can be accomplished using browser developer tools, proxy interceptors like Burp Suite, or direct HTTP request manipulation.

The vulnerability mechanism involves parameter manipulation in the sales form submission. An attacker can submit negative values for the txtprice and txttotalcost fields, causing the application to process these invalid amounts and record them in the database. For detailed technical information and proof of concept, refer to the GitHub PoC Repository.

Detection Methods for CVE-2026-30573

Indicators of Compromise

• Sales records containing negative price values in the database
• Unusual discrepancies in daily or monthly financial reports showing unexpected credits
• Transaction logs showing sales with negative txtprice or txttotalcost values
• Abnormal HTTP POST requests to add-sales.php with negative numeric parameters

Detection Strategies

• Implement database queries to audit sales records for negative price or total cost values
• Deploy web application firewalls (WAF) with rules to detect and block negative numeric values in price-related parameters
• Enable application logging to capture all transaction submissions with parameter values for forensic analysis
• Perform regular financial reconciliation to identify discrepancies between expected and actual revenue

Monitoring Recommendations

• Monitor web server access logs for unusual patterns of POST requests to add-sales.php
• Set up database triggers or scheduled audits to alert on negative monetary values in transaction tables
• Implement real-time alerting for financial anomalies such as refunds exceeding a threshold or negative daily totals
• Review application logs periodically for signs of parameter tampering or exploitation attempts

How to Mitigate CVE-2026-30573

Immediate Actions Required

• Implement server-side validation to reject negative values for txtprice and txttotalcost parameters
• Audit existing sales records in the database to identify and remediate any fraudulent transactions with negative values
• Restrict access to the sales functionality to authorized users only and implement proper authentication controls
• Consider taking the affected application offline until proper input validation can be implemented

Patch Information

No official vendor patch is currently available for SourceCodester Pharmacy Product Management System 1.0. Organizations should implement custom mitigations or consider alternative software solutions. Monitor the GitHub PoC Repository for updates and additional technical details.

Workarounds

• Add server-side input validation in add-sales.php to ensure txtprice and txttotalcost values are greater than or equal to zero
• Implement database constraints to reject INSERT or UPDATE operations with negative monetary values
• Deploy a web application firewall with custom rules to filter requests containing negative price parameters
• Implement application-level access controls to limit who can create sales transactions

# Example server-side validation (PHP)
if (isset($_POST['txtprice']) && $_POST['txtprice'] < 0) {
    die("Error: Price cannot be negative");
}
if (isset($_POST['txttotalcost']) && $_POST['txttotalcost'] < 0) {
    die("Error: Total cost cannot be negative");
}