CVE-2026-35868 in Router AC2100_AZ3
Summary
by MITRE • 08/27/2026
A Command Injection vulnerability exists in the bs_SetLimitCli_info function within the libshare.so library of LB-link Router AC2100_AZ3 V1.0.4. This flaw occurs due to insufficient validation and sanitization of user-supplied input before it is passed to a system-level command execution context. An attacker can exploit this vulnerability by injecting specially crafted shell metacharacters or payloads into the vulnerable parameter, resulting in the execution of arbitrary operating system commands.
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Analysis
by VulDB Data Team • 08/27/2026
The identified vulnerability represents a critical Command Injection flaw located within the bs_SetLimitCli_info function of the libshare.so library associated with LB-link Router AC2100_AZ3 V1.0.4. This specific component is responsible for managing client connection limits and related network policies, making it a high-value target for attackers seeking to gain unauthorized control over the device's underlying operating system. The root cause of this vulnerability lies in the fundamental failure of input validation and sanitization mechanisms within the application logic. When user-supplied data is received by the bs_SetLimitCli_info function, the software fails to adequately filter or escape special shell metacharacters before passing these inputs into a context where they are executed as part of system-level commands. This lack of rigorous boundary checking allows malicious actors to bypass intended functional constraints and inject arbitrary code that the operating system will execute with the privileges of the vulnerable process.
From an operational perspective, this vulnerability poses a severe risk to network security and device integrity. An attacker who can exploit this flaw does not merely gain access to application-level features but achieves remote command execution on the router itself. This capability effectively compromises the confidentiality, integrity, and availability of the entire local area network connected through the device. The impact extends beyond simple data exfiltration; it allows for complete system takeover, enabling the attacker to install persistent backdoors, pivot into other internal networks, or disrupt service by terminating critical processes. Given that routers often serve as the primary gateway between a private network and the public internet, compromising this component can lead to widespread reconnaissance of internal assets and potential lateral movement across connected devices.
This vulnerability is technically classified under Common Weakness Enumeration identifier CWE-78, which defines Improper Neutralization of Special Elements used in an OS Command, commonly known as OS Command Injection. The exploitation technique aligns with the MITRE ATT&CK framework tactic T1059, specifically subtechnique 004 for Command and Scripting Interpreter abuse. By injecting shell metacharacters such as semicolons, pipes, or ampersands into the vulnerable parameter, an attacker can chain commands to execute arbitrary scripts or binaries on the host system. The absence of input sanitization means that even simple payloads can result in full command execution, highlighting a critical deficiency in secure coding practices during the development and deployment of embedded firmware for networking hardware.
Mitigation strategies must address both immediate remediation and long-term security posture improvements. For administrators currently running vulnerable versions, the primary recommendation is to apply vendor-provided firmware updates that patch this specific flaw within the libshare.so library if available. In cases where patches are not immediately accessible, network segmentation should be implemented to restrict access to the router's management interface from untrusted networks. Additionally, deploying intrusion detection systems capable of identifying command injection patterns in HTTP or API traffic can provide an additional layer of defense against exploitation attempts. For developers and vendors, this incident underscores the necessity of implementing strict input validation frameworks that whitelist allowed characters rather than relying on blacklist approaches, as well as utilizing safe system APIs that do not invoke shell interpreters directly when processing user data.