CVE-2025-46736 in Umbraco
Summary
by MITRE • 05/06/2025
Umbraco is a free and open source .NET content management system. Prior to versions 10.8.10 and 13.8.1, based on an analysis of the timing of post login API responses, it's possible to determine whether an account exists. The issue is patched in versions 10.8.10 and 13.8.1. No known workarounds are available.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability identified as CVE-2025-46736 affects Umbraco content management systems prior to versions 10.8.10 and 13.8.1, representing a significant security weakness that undermines the system's authentication security model. This issue stems from timing variations in API response handling during the login process, which creates a side-channel attack vector that allows malicious actors to determine account existence through careful analysis of response times. The flaw specifically impacts the post-login API endpoint where the system's behavior differs between existing and non-existing user accounts, providing attackers with information that could facilitate subsequent authentication attacks or account enumeration activities.
The technical implementation of this vulnerability resides in the authentication response handling mechanism within Umbraco's API layer. When processing login requests, the system exhibits different timing characteristics based on whether the submitted username exists in the user database, creating a measurable timing difference that can be exploited through automated timing attacks. This behavior violates fundamental security principles for authentication systems and directly relates to CWE-204, which addresses information exposure through timing differences. The vulnerability operates at the application layer and specifically affects the authentication flow, making it particularly dangerous for systems that rely on Umbraco for content management and user access control.
The operational impact of this vulnerability extends beyond simple account enumeration, as it provides attackers with critical information that can be leveraged in broader attack strategies. An attacker can systematically test multiple usernames against the login endpoint to identify valid accounts, which then enables more sophisticated attacks such as password spraying, credential stuffing, or targeted brute force attempts. This vulnerability particularly affects organizations using Umbraco for public-facing websites or applications where user enumeration could lead to unauthorized access attempts and potential data breaches. The timing-based approach makes this attack relatively simple to implement and can be automated, increasing the threat surface for affected systems.
Mitigation strategies for CVE-2025-46736 require immediate deployment of the patched versions 10.8.10 and 13.8.1, which address the timing inconsistencies in the authentication response handling. Organizations should prioritize updating their Umbraco installations to prevent exploitation, as no effective workarounds exist for this particular vulnerability. The fix implements consistent response timing regardless of account existence, eliminating the timing side-channel that enabled the attack. Security teams should also consider implementing additional authentication controls such as account lockout mechanisms, rate limiting on authentication endpoints, and monitoring for unusual login patterns that could indicate enumeration attempts. From an ATT&CK perspective, this vulnerability maps to techniques involving credential access through information discovery and privilege escalation, making it particularly relevant for organizations implementing comprehensive threat hunting and incident response procedures.