CVE-2021-3694 in LedgerSMB
Summary
by MITRE • 08/23/2021
LedgerSMB does not sufficiently HTML-encode error messages sent to the browser. By sending a specially crafted URL to an authenticated user, this flaw can be abused for remote code execution and information disclosure.
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Analysis
by VulDB Data Team • 07/21/2025
The vulnerability identified as CVE-2021-3694 affects LedgerSMB, an open-source accounting software application that processes financial transactions for businesses and organizations. This weakness resides in the application's insufficient HTML encoding of error messages that are transmitted to web browsers, creating a critical security gap that can be exploited by malicious actors. The flaw specifically impacts how the system handles error conditions during user interactions, particularly when processing URLs that contain crafted payloads designed to bypass security controls.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize error message content before rendering it within the browser context. When an authenticated user accesses a specially crafted URL, the system processes the malformed input without adequate HTML encoding, allowing malicious code embedded within error messages to execute in the victim's browser environment. This represents a classic cross-site scripting vulnerability that has been escalated to enable remote code execution capabilities, making it particularly dangerous for enterprise environments where sensitive financial data is processed.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the ability to execute arbitrary code on affected systems. Attackers can leverage this flaw to establish persistent access to financial systems, potentially leading to data breaches, financial fraud, and unauthorized transactions. The authenticated nature of the attack means that adversaries must first gain valid user credentials, but once obtained, the vulnerability allows for significant compromise of the application's security posture and the underlying data it protects.
Organizations utilizing LedgerSMB should implement immediate mitigations including updating to patched versions of the application, implementing web application firewalls to detect and block malicious URL patterns, and conducting thorough security assessments of their financial systems. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and maps to ATT&CK technique T1059.007 for command and script interpreter execution. Additional protective measures include implementing content security policies, regular security monitoring, and user access controls to minimize the attack surface and prevent unauthorized access to financial applications.