Weakness (CWE)
CWE-203: Observable Discrepancy
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
How to prevent it (2 mitigations)
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Architecture and Design
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
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Implementation
Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended). The messages should not reveal the methods that were used to determine the error. Attackers can use detailed information to refine or optimize their original attack, thereby increasing their chances of success.
If errors must be captured in some detail, record them in log messages, but consider what could occur if the log messages can be viewed by attackers. Highly sensitive information such as passwords should never be saved to log files.
Avoid inconsistent messaging that might accidentally tip off an attacker about internal state, such as whether a user account exists or not.
Source: MITRE CWE-203
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Medium 5.3CVE-2026-37064 Public exploit
User enumeration in /vfm-admin/ajax/usr-check.php in Veno File Manager Project 4.4.9 allows an unauthenticated attacker…
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Medium 5.3CVE-2024-55374 Public exploit
REDCap 14.3.13 allows an attacker to enumerate usernames due to an observable discrepancy between login attempts.
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Medium 5.5CVE-2025-48561 Public exploit
In multiple locations, there is a possible way to access data displayed on the screen due to side channel information d…
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Medium 5.3CVE-2025-24011 Public exploit
Umbraco CMS Vulnerable to User Enumeration Feasible Based On Management API Timing and Response Codes
Umbraco is a free and open source .NET content management system. Starting in version 14.0.0 and prior to versions 14.3.2 and 15.1.2, it's possible to determine whether an account exists based on an analysis of response codes and timing of Umbraco management …
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Medium 5.3CVE-2024-48644 Public exploit
Accounts enumeration vulnerability in the Login Component of Reolink Duo 2 WiFi Camera (Firmware Version v3.0.0.1889_23…
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Medium 5.3CVE-2023-47102 Public exploit
UrBackup Server 2.5.31 allows brute-force enumeration of user accounts because a failure message confirms that a userna…
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Medium 4.8CVE-2023-3897 Public exploit
Bypassing CAPTCHA & Enumerating Usernames via Password Reset Page
Username enumeration is possible through Bypassing CAPTCHA in On-premise SureMDM Solution on Windows deployment allows attacker to enumerate local user information via error message. This issue affects SureMDM On-premise: 6.31 and below version
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Medium 5.3CVE-2023-30458 Public exploit
A username enumeration issue was discovered in Medicine Tracker System 1.0. The login functionality allows a malicious …
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Medium 6.5CVE-2022-34125 Public exploit
front/icon.send.php in the CMDB plugin before 3.0.3 for GLPI allows attackers to gain read access to sensitive informat…
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Medium 5.9
Timing Oracle in RSA Decryption
A timing based side channel exists in the OpenSSL RSA Decryption implementation which could be sufficient to recover a plaintext across a network in a Bleichenbacher style attack. To achieve a successful decryption an attacker would have to be able to send a …
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Medium 5.3CVE-2016-20012 Public exploit
OpenSSH through 8.7 allows remote attackers, who have a suspicion that a certain combination of username and public key…
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Medium 5.3CVE-2021-21424 Public exploit
Prevent user enumeration using Guard or the new Authenticator-based Security
Symfony is a PHP framework for web and console applications and a set of reusable PHP components. The ability to enumerate users was possible without relevant permissions due to different handling depending on whether the user existed or not when attempting t…
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Medium 5.5
Systems with microprocessors utilizing speculative execution and speculative execution of memory reads before the addre…
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Medium 5.6
Systems with microprocessors utilizing speculative execution and indirect branch prediction may allow unauthorized disc…
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Medium 5.6
Systems with microprocessors utilizing speculative execution and branch prediction may allow unauthorized disclosure of…