CVE-2026-111386 in Nezha
Summary
by MITRE • 10/16/2026
Nezha from 1.7.0 before 2.3.15 contains an information disclosure vulnerability that allows authenticated members to enumerate other tenants' server IDs through differential responses. Attackers can sweep sequential IDs against getServerConfig and setServerConfig, distinguishing 'permission denied' from success payloads to map other users' servers.
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Analysis
by VulDB Data Team • 10/16/2026
The identified security flaw within Nezha versions ranging from 1.7.0 up to but not including 2.3.15 represents a classic information disclosure vulnerability rooted in improper access control and insufficient input validation mechanisms. This specific weakness allows authenticated members, who possess valid credentials for their own tenant account, to exploit the application's response behavior to enumerate server identifiers belonging to other tenants within the same deployment instance. The core of the technical flaw lies in how the backend handles requests directed at endpoints such as getServerConfig and setServerConfig when provided with sequential or guessed Server IDs that do not belong to the requesting user. Instead of returning a uniform error code indicating unauthorized access regardless of whether the ID exists, the application exhibits differential responses based on the existence and ownership status of the target resource.
This discrepancy in response payloads creates an enumeration vector that attackers can leverage through automated scanning techniques. By systematically sweeping sequential Server IDs against these endpoints, an attacker can distinguish between different types of failure states. Specifically, a request targeting a non-existent ID might return one type of error or timeout, while a request targeting an existing ID owned by another tenant returns a distinct permission denied message. This binary distinction in the application's feedback loop effectively allows the adversary to map out which server IDs are active and associated with other tenants without needing direct access to those accounts. The vulnerability is particularly dangerous because it transforms what might appear as simple authentication errors into a reconnaissance tool for lateral movement or further exploitation within multi-tenant environments where isolation between tenant data is critical.
From an operational impact perspective, this information disclosure can lead to significant privacy violations and increased attack surface exposure in managed hosting or monitoring scenarios. Nezha typically functions as a server monitoring agent, meaning that knowing the Server IDs of other tenants reveals structural details about their infrastructure layout. This knowledge enables attackers to prioritize specific targets for subsequent attacks, such as attempting to exploit known vulnerabilities associated with those specific server configurations or initiating targeted denial-of-service campaigns against identified assets. Furthermore, in environments where tenant isolation is a primary security requirement, this flaw undermines the fundamental trust model of the multi-tenant architecture, potentially leading to regulatory non-compliance if sensitive operational data is inadvertently exposed through such enumeration techniques.
The vulnerability aligns with CWE-209, which describes an information exposure through an error message that reveals implementation details, and more broadly falls under CWE-613, insufficient session expiration or termination, as it exploits the persistence of authenticated sessions to probe for unauthorized resources. In terms of MITRE ATT&CK mapping, this behavior corresponds to T1589.002, Credential Guessing, although in this context it is adapted for identifier enumeration rather than password guessing, and closely relates to T1486, Data Encrypted for Impact, if the enumerated IDs are used as a precursor to ransomware deployment or destructive actions against identified targets. It also reflects aspects of T1078, Valid Accounts, by leveraging legitimate credentials to perform unauthorized reconnaissance activities that exceed the intended scope of those accounts.
To mitigate this vulnerability and prevent further exploitation, immediate action is required for all systems running Nezha versions prior to 2.3.15. The primary remediation step is to upgrade the software to version 2.3.15 or later, where the developers have addressed the differential response logic by ensuring that requests for resources outside of a user's authorized scope return consistent and non-informative error messages regardless of whether the target resource exists in the system. In addition to upgrading, organizations should implement strict input validation on all server-side endpoints to ensure that any Server ID provided is strictly validated against an allowlist associated with the authenticated user's tenant context before processing begins. Network-level controls such as Web Application Firewalls can also be configured to detect and block rapid sequential requests targeting different resource IDs, which would indicate automated enumeration attempts. Regular security audits focusing on access control logic and response consistency are recommended to identify similar flaws in other parts of the application stack that may not have been covered by this specific patch.