CVE-2025-13953 is an authentication bypass vulnerability classified under CWE-290, found in the GTT Sistema de Información Tributario, a tax information system widely used for managing tax data and authentication via Active Directory (LDAP). The vulnerability stems from the application’s use of a local WebSocket to perform authentication, where the application fails to properly validate the authenticity or origin of the data received through this channel. This design flaw allows an attacker who has access to the local machine or internal network to spoof the WebSocket connection, injecting manipulated authentication data. Consequently, the attacker can impersonate any user within the domain without needing valid credentials, effectively bypassing all authentication controls. This leads to a full compromise of the system’s confidentiality, integrity, and availability, as attackers could access sensitive tax information, alter records, or disrupt services. The vulnerability affects all versions of the product and has been assigned a CVSS 4.0 score of 9.3, reflecting its critical severity with network attack vector, no required privileges or user interaction, and high impact on all security properties. Although no exploits are known in the wild yet, the vulnerability’s nature and the criticality of the affected system make it a high-priority risk. The lack of available patches increases the urgency for mitigation through compensating controls and monitoring.

For European organizations, especially governmental tax authorities and entities relying on the GTT Sistema de Información Tributario, this vulnerability poses a severe risk. Exploitation could lead to unauthorized access to highly sensitive tax data, including personal and financial information of individuals and businesses, resulting in privacy violations and potential financial fraud. Integrity of tax records could be compromised, undermining trust in tax administration and potentially causing incorrect tax assessments or loss of revenue. Availability could also be impacted if attackers disrupt authentication services or the application itself, leading to operational downtime. Given the critical role of tax systems in national infrastructure, a successful attack could have cascading effects on public administration and economic stability. The vulnerability’s exploitation requires only internal or local access, which means insider threats or lateral movement by attackers who have breached perimeter defenses could trigger a full domain compromise. This elevates the risk profile for European organizations that have integrated this system within their IT infrastructure.

Immediate mitigation should focus on restricting access to the local machine and internal network segments where the GTT Sistema de Información Tributario is deployed, employing strict network segmentation and access controls to limit exposure. Organizations should implement enhanced monitoring and logging of WebSocket connections and authentication attempts to detect anomalous or spoofed traffic. Deploying endpoint protection and intrusion detection systems to identify suspicious local activities is critical. Until an official patch is released, consider disabling or restricting the use of the vulnerable WebSocket authentication mechanism if feasible, or replacing it with a more secure authentication method that includes strong validation of data origin and integrity. Conduct thorough audits of user accounts and domain privileges to minimize the impact of potential impersonation. Additionally, enforce multi-factor authentication (MFA) at the domain level to add a layer of defense against unauthorized access. Organizations should maintain close communication with GTT for updates and patches and prepare incident response plans tailored to this vulnerability.