CVE-2026-112352 in SureLine
Summary
by MITRE • 10/27/2026
Sunhillo SureLine before 9.1.5 contains an authentication bypass vulnerability that allows an unauthenticated remote attacker to impersonate any user with an active web session by forging a session cookie containing only a cleartext username with no random identifier or integrity protection. Attackers can guess default account names such as Admin or sftp_user and submit a forged username cookie to satisfy the login check in checkLogin (libwebcmn.so) and networkDiag.cgi, chaining into root command execution.
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Analysis
by VulDB Data Team • 10/27/2026
The vulnerability identified within Sunhillo SureLine versions prior to 9.1.5 represents a critical authentication bypass flaw rooted in flawed session management practices. The core technical deficiency lies in the application's handling of web sessions, specifically how it validates user identity through cookies. Instead of employing cryptographically secure random identifiers or integrity checks such as message authentication codes, the system relies on a cleartext username stored directly within the session cookie. This design choice fundamentally undermines the security model because it removes any mechanism to verify that the session token was issued by the server and has not been tampered with by an external party. Consequently, the application treats any provided username in this specific cookie format as valid proof of authentication, effectively allowing an attacker to assume the identity of any user who currently holds an active web session on the target system.
From a technical perspective, the exploitation vector targets two primary components: libwebcmn.so and networkDiag.cgi. The checkLogin function within libwebcmn.so serves as the gatekeeper for authentication states, while networkDiag.cgi likely exposes administrative or diagnostic functionalities that require elevated privileges. By crafting a malicious HTTP request containing a forged cookie with only a cleartext username field, an unauthenticated remote attacker can bypass these checks entirely. The absence of random identifiers means there is no entropy to prevent prediction, and the lack of integrity protection ensures that the server cannot detect if the session data has been modified outside its control. This flaw aligns directly with CWE-287, which describes Improper Authentication, as well as CWE-613, Insufficient Session Expiration, because the system fails to enforce robust state validation mechanisms required for secure web applications.
The operational impact of this vulnerability is severe due to the potential for privilege escalation and remote code execution. Attackers can easily guess common default account names such as Admin or sftp_user, which are frequently used in industrial control systems and network devices. Once a valid username is identified through brute force or enumeration, submitting it via the forged cookie grants immediate access without requiring a password. This bypass allows the attacker to chain into root command execution capabilities available within the diagnostic interfaces. The ability to execute commands with root privileges effectively compromises the entire system integrity, allowing for complete control over the device's configuration, network settings, and potentially other connected systems in an industrial or enterprise environment.
This exploitation path is consistent with MITRE ATT&CK techniques related to Initial Access and Privilege Escalation. Specifically, it mirrors T1078 Valid Accounts, where attackers use legitimate credentials or impersonate users to gain access without triggering typical intrusion detection alerts associated with failed login attempts. Furthermore, the ability to execute root commands post-exploitation aligns with T1068 Exploitation for Privilege Escalation and potentially T1059 Command and Scripting Interpreter if arbitrary code execution is achieved through the diagnostic interface. The lack of input validation on session tokens also touches upon CWE-20 Improper Input Validation, as the application accepts untrusted data from the client side without sufficient sanitization or verification against server-side state.
Mitigation strategies must focus on immediate patching and architectural remediation. Organizations running Sunhillo SureLine versions before 9.1.5 should apply the vendor-provided update immediately to address this critical flaw. In addition to upgrading, administrators should enforce strong password policies for all default accounts such as Admin and sftp_user to reduce the success rate of username guessing attacks during any window where patches are not yet applied. Network segmentation is also recommended to limit exposure of management interfaces like networkDiag.cgi to trusted IP ranges only. From a development standpoint, future implementations must utilize secure session identifiers generated with sufficient entropy and implement integrity checks such as HMACs or signed tokens to ensure that session data cannot be forged by external actors.