CVE-2026-42840 in ERPNext
Summary
by MITRE • 06/03/2026
An authenticated user can persist arbitrary HTML/JavaScript in the email_id or mobile_no fields of a Customer record and trigger unescaped rendering in the Point of Sale (POS) interface for every operator who selects that customer. This issue affects ERPNext: 16.16.0.
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Analysis
by VulDB Data Team • 06/03/2026
This vulnerability represents a critical server-side request forgery and cross-site scripting flaw that undermines the security integrity of ERPNext's customer management system. The issue stems from inadequate input validation and output sanitization mechanisms within the customer record handling functionality, specifically affecting the email_id and mobile_no fields. When an authenticated user submits malicious HTML or JavaScript code through these fields, the system fails to properly escape or sanitize the content, allowing the malicious payload to persist within the database. The vulnerability is particularly dangerous because it leverages the Point of Sale interface as the attack vector, where every operator who interacts with the compromised customer record will encounter the malicious code execution.
The technical exploitation of this vulnerability follows a well-established pattern of persistent cross-site scripting attacks, where the malicious content is stored server-side and then rendered client-side without proper sanitization. This creates a scenario where the attacker can execute arbitrary JavaScript code within the context of the POS interface, potentially leading to session hijacking, data exfiltration, or further compromise of the affected system. The vulnerability manifests through the improper handling of user input during the rendering process, where the system assumes that the stored data is safe for direct display without additional validation or escaping mechanisms. This flaw aligns with common weakness enumerations such as CWE-79, which addresses cross-site scripting vulnerabilities, and CWE-20, which covers input validation issues.
The operational impact of this vulnerability extends beyond simple data corruption, as it provides attackers with a persistent foothold within the ERPNext environment. Every POS operator who selects the compromised customer record becomes a potential victim of the malicious payload, creating a widespread attack surface that could affect multiple users simultaneously. The attack chain typically involves an authenticated user leveraging their privileges to inject malicious content, followed by unsuspecting operators who unknowingly trigger the payload during normal POS operations. This vulnerability particularly threatens the integrity of customer data and the security of the entire point-of-sale ecosystem, as it allows attackers to manipulate the user interface and potentially access sensitive business information.
Mitigation strategies should focus on implementing comprehensive input validation and output sanitization measures throughout the application's data processing pipeline. The system must enforce strict validation of email and mobile number fields to prevent the injection of HTML or JavaScript content, while also implementing proper escaping mechanisms when rendering customer data within the POS interface. Organizations should consider implementing content security policies, input filtering at multiple layers, and regular security audits of data handling processes. The solution aligns with ATT&CK framework techniques related to command and control through web shell deployment and credential access through session hijacking. Additionally, implementing proper access controls and monitoring mechanisms can help detect unusual activities that might indicate exploitation attempts, while regular patching and security updates ensure that known vulnerabilities are addressed promptly.