CVE-2019-7550 in jforum
Summary
by MITRE
In JForum 2.1.8, an unauthenticated, remote attacker can enumerate whether a user exists by using the "create user" function. If a register/check/username?username= request corresponds to a username that exists, then an "is already in use" error is produced. NOTE: this product is discontinued.
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Analysis
by VulDB Data Team • 07/10/2023
The vulnerability identified as CVE-2019-7550 affects JForum version 2.1.8, representing a critical information disclosure flaw that undermines user account security through improper validation mechanisms. This issue stems from the application's lack of proper input sanitization and account validation controls within its user registration system, creating a significant attack surface that allows remote threat actors to gather intelligence about existing user accounts without authentication. The vulnerability manifests through the application's username validation process, where the system provides different responses based on whether a requested username already exists in the database, effectively leaking information about legitimate user accounts.
The technical implementation of this flaw occurs within the application's user registration endpoint, specifically when processing requests to check username availability through the register/check/username?username= parameter. When an attacker submits a username that does not exist, the system typically returns a success response indicating the username is available. However, when the submitted username corresponds to an existing account, the application responds with an "is already in use" error message, creating a clear distinction between valid and invalid usernames. This behavior directly violates security principles by providing differential responses that enable account enumeration attacks, a technique commonly categorized under CWE-200 Information Exposure.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data that can be leveraged for subsequent attacks. Security researchers and threat actors can systematically test usernames to identify valid accounts within the system, potentially enabling targeted attacks such as credential stuffing, brute force attempts, or social engineering campaigns. The vulnerability operates at the application layer and requires no authentication, making it particularly dangerous as it allows attackers to gather intelligence from publicly accessible endpoints without requiring any prior access credentials. This type of vulnerability is often categorized under the ATT&CK framework as part of the reconnaissance phase, specifically falling under techniques related to credential access and enumeration.
The implications of this vulnerability are particularly severe given that JForum 2.1.8 is a discontinued product, meaning that no official security updates or patches are available to address this flaw. Organizations that continue to operate this outdated version face increased risk exposure, as the vulnerability cannot be remediated through standard patch management processes. The lack of vendor support compounds the security risk, as administrators cannot rely on official security advisories or mitigation guidance from the software vendor. This scenario exemplifies the dangers of operating legacy software systems and highlights the importance of proper software lifecycle management and timely upgrades to prevent exploitation of known vulnerabilities. The vulnerability represents a classic case of insufficient input validation and output sanitization, where the application's response behavior inadvertently reveals sensitive information about its user base, creating a pathway for attackers to identify and target legitimate accounts within the system.