CVE-2020-10102 in Zammad
Summary
by MITRE
An issue was discovered in Zammad 3.0 through 3.2. The Forgot Password functionality is implemented in a way that would enable an anonymous user to guess valid user emails. In the current implementation, the application responds differently depending on whether the input supplied was recognized as associated with a valid user. This behavior could be used as part of a two-stage automated attack. During the first stage, an attacker would iterate through a list of account names to determine which correspond to valid accounts. During the second stage, the attacker would use a list of common passwords to attempt to brute force credentials for accounts that were recognized by the system in the first stage.
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Analysis
by VulDB Data Team • 04/09/2024
The vulnerability identified as CVE-2020-10102 affects Zammad versions 3.0 through 3.2 and represents a critical security flaw in the password recovery mechanism that enables account enumeration attacks. This issue stems from the application's inconsistent response behavior when processing forgot password requests, creating a timing or response-based side channel that reveals information about user account validity. The flaw directly violates security principles of defensive design and proper error handling, as it provides attackers with actionable intelligence about legitimate user accounts without requiring authentication credentials.
The technical implementation of this vulnerability resides in the application's password reset functionality where the system differentiates its responses between valid and invalid email addresses. When a user submits a password reset request, the application returns distinct responses based on whether the email address corresponds to an existing account. This differential response pattern creates a predictable information leakage that an attacker can exploit through automated tools. The vulnerability maps to CWE-200, which describes information exposure through improper error handling, and demonstrates poor implementation of the principle of least privilege by revealing account existence information to unauthenticated users.
The operational impact of this vulnerability is significant as it enables automated account enumeration attacks that can be executed with minimal technical expertise. Attackers can systematically test email addresses against the password reset endpoint to identify valid user accounts, effectively creating a user directory that would normally require legitimate access credentials or social engineering to obtain. This enumeration capability serves as a crucial first step for subsequent credential brute force attacks, dramatically reducing the search space for password guessing operations. The vulnerability aligns with ATT&CK technique T1078.004, which covers valid accounts obtained through credential access, by providing attackers with a method to identify and validate legitimate user accounts.
The attack vector operates through a two-stage process that leverages the application's inconsistent response behavior. During the initial reconnaissance phase, attackers can rapidly iterate through potential email addresses to determine which ones correspond to valid accounts within the Zammad system. This stage typically involves sending multiple password reset requests and analyzing the responses for differences in timing, error messages, or response codes. The second phase involves using the validated account list to conduct targeted brute force attacks against the identified accounts, making credential compromise significantly more likely. The vulnerability essentially provides attackers with a low-effort method to identify valid targets for more sophisticated attacks.
Organizations using affected Zammad versions should implement immediate mitigations to address this vulnerability by ensuring that the password reset functionality provides consistent responses regardless of whether the email address exists in the system. This approach eliminates the information leakage that enables account enumeration attacks and aligns with security best practices outlined in OWASP Top Ten and NIST cybersecurity frameworks. The fix should involve implementing constant-time response handling, where the application responds identically to all password reset requests, thereby preventing attackers from distinguishing between valid and invalid email addresses through response analysis. Additionally, organizations should consider implementing rate limiting and account lockout mechanisms to further protect against automated attack attempts while maintaining legitimate user access to password recovery features.