CVE-2025-15681 in TLogger
Summary
by MITRE • 08/10/2026
TBEA TLogger V2.1.0.0B0.0.0.0 contains an authentication bypass in its web server. After a user has previously authenticated to the device, an unauthenticated attacker can directly access protected functionality through the /index.asp endpoint without providing valid credentials. This allows the attacker to access functionality intended for authenticated users and may expose or modify device configuration and data. Logging out from the bypassed state can additionally cause the web server to crash.
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Analysis
by VulDB Data Team • 08/10/2026
The TBEA TLogger V2.1.0.0 web server implementation contains a critical authentication bypass vulnerability that fundamentally undermines the device's security model. This flaw exists within the authentication mechanism design where previously authenticated sessions are not properly invalidated or validated when accessing protected endpoints. The vulnerability specifically manifests through the /index.asp endpoint which should require proper authentication but instead allows unauthenticated access to privileged functionality. This represents a classic case of improper authentication handling that violates fundamental security principles and creates an attack vector for privilege escalation.
The technical implementation flaw stems from inadequate session management and access control validation within the web server framework. When users authenticate to the device, their credentials are accepted but the system fails to properly enforce authorization checks on subsequent requests to protected resources. The /index.asp endpoint serves as a gateway to administrative functions that should only be accessible to authenticated users with appropriate privileges. This vulnerability falls under CWE-287 which specifically addresses improper authentication issues, and aligns with ATT&CK technique T1078 for valid accounts and T1566 for credential harvesting through application vulnerabilities.
The operational impact of this authentication bypass is severe and multifaceted as attackers can directly access sensitive device configuration data, modify system parameters, and potentially exfiltrate confidential information without ever providing valid credentials. The vulnerability exposes the underlying device architecture to unauthorized manipulation, allowing attackers to compromise the integrity and confidentiality of the logging system. Additionally, the web server exhibits unstable behavior when users attempt to log out from the bypassed state, leading to potential denial-of-service conditions that can disrupt legitimate operations and make the device temporarily inaccessible.
Organizations deploying TBEA TLogger devices must implement immediate mitigations to address this vulnerability. The primary recommendation involves patching the firmware to properly enforce authentication checks on all protected endpoints, particularly the /index.asp resource. Network segmentation should be implemented to limit direct access to administrative interfaces, while monitoring systems should be deployed to detect unusual access patterns or unauthorized configuration changes. Security teams should also consider implementing additional authentication layers such as two-factor authentication and regular security assessments to identify similar vulnerabilities in other networked devices. The vulnerability demonstrates the critical importance of proper session management and access control implementation in embedded web servers, as highlighted by industry standards that emphasize the need for robust authentication mechanisms to prevent unauthorized system access.