CVE-2026-82043 in UTMStack
Summary
by MITRE • 10/03/2026
UTMStack before 11.2.16 contains an account enumeration vulnerability that allows unauthenticated attackers to determine registered email addresses by observing differing HTTP responses from the POST /api/account/reset-password/init endpoint. Attackers can submit arbitrary email addresses and distinguish registered accounts, which return 200 OK, from unregistered accounts, which trigger a 500 Internal Server Error with backend error details, enabling targeted phishing or credential attacks.
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Analysis
by VulDB Data Team • 10/03/2026
The vulnerability identified in UTMStack versions prior to 11.2.16 represents a classic account enumeration flaw rooted in inconsistent application behavior during password reset operations. This security defect is located specifically within the POST /api/account/reset-password/init endpoint, which serves as the entry point for users initiating a password recovery process. The core technical issue lies in how the backend system handles requests containing email addresses that do not correspond to any registered user account versus those that do. Instead of providing a uniform response regardless of whether the email exists in the database, the application exhibits divergent HTTP status codes and error handling mechanisms based on the existence of the target account. This inconsistency creates a reliable side-channel through which an unauthenticated attacker can probe the system without needing valid credentials or prior access to user data.
From a technical perspective, when an attacker submits an email address that is registered within the UTMStack environment, the server processes the request successfully and returns an HTTP 200 OK status code. This response typically indicates that the password reset token has been generated and sent via email, confirming the presence of the account in the system's directory. Conversely, when a non-existent or unregistered email address is submitted, the application fails to handle this edge case gracefully within its business logic layer. Instead of returning a generic success message similar to the registered case, the backend encounters an internal exception and returns an HTTP 500 Internal Server Error. Crucially, this error response often includes verbose backend error details or stack traces that are exposed in the body of the response. This leakage of technical information not only confirms the non-existence of the account but also provides attackers with additional intelligence regarding the underlying technology stack, framework versions, and potential code structures, thereby amplifying the severity of the vulnerability beyond simple enumeration.
The operational impact of this vulnerability is significant as it facilitates targeted social engineering attacks at scale. By automating requests to the affected endpoint using tools such as Burp Suite or custom scripts, an attacker can rapidly map out a list of valid email addresses associated with UTMStack users within an organization. This capability transforms generic phishing campaigns into highly personalized spear-phishing attempts. With knowledge of which employees hold active accounts, attackers can craft messages that appear more legitimate and urgent, increasing the likelihood of successful credential theft or malware installation. Furthermore, the exposure of backend error details in the 500 responses adds a secondary risk vector by aiding reconnaissance efforts, allowing adversaries to identify specific software components for further exploitation using known exploits tailored to those versions.
This vulnerability aligns with CWE-204, which defines Responsive Discrepancy as an observable difference in response when processing input that indicates success versus failure of the operation. It also maps directly to MITRE ATT&CK technique T1589.001, specifically Gather Victim Email Addresses under the Initial Access phase, where attackers collect email addresses from various sources including application responses. The lack of consistent error handling is a common anti-pattern in web development that security teams must actively mitigate during code reviews and penetration testing phases.
To remediate this issue, it is imperative to upgrade UTMStack to version 11.2.16 or later, where the vendor has addressed these inconsistencies. For organizations unable to immediately patch due to operational constraints, several mitigation strategies can be employed at the network perimeter. Implementing a Web Application Firewall (WAF) rule set that monitors for HTTP 500 responses triggered by POST requests to the password reset endpoint can help detect and block automated enumeration attempts in real-time. Additionally, configuring rate limiting on this specific API endpoint will slow down brute-force style attacks, making large-scale enumeration impractical within reasonable timeframes. From a development standpoint, future implementations must ensure that all user-facing endpoints return identical responses for both valid and invalid inputs regarding account existence checks. This includes suppressing detailed error messages in production environments to prevent information leakage while maintaining functional parity between successful and failed password reset requests.