Description

CAYIN CMS-WS, CMS-SE, and SMP series products developed by CAYIN Technology have an Arbitrary File Upload vulnerability. Privileged remote attackers can upload and execute web shells backdoors, thereby enabling arbitrary code execution on the server.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.2",
  "pubDate": "2026-08-26T09:16:48.717Z",
  "pubdate": "2026-08-26T09:16:48.717Z",
  "executiveSummary": "CAYIN CMS-WS, CMS-SE, and SMP series products are susceptible to an Arbitrary File Upload vulnerability that facilitates Remote Code Execution (RCE).\nThis vulnerability originates from improper validation of user-supplied files, allowing authenticated attackers with sufficient privileges to upload malicious web shell scripts to the server.\nThe successful exploitation of this flaw enables an adversary to bypass security controls and execute arbitrary code within the context of the web server service account.\nThe impact includes full server compromise, unauthorized access to sensitive data, and the potential for lateral movement within the network infrastructure.\nExploitation requires the attacker to possess valid administrative or elevated privileges, significantly limiting the attack surface to malicious insiders or attackers who have previously compromised valid administrator credentials.\nGiven the nature of the vulnerability, the integrity, confidentiality, and availability of the affected CAYIN systems are considered at high risk.",
  "technicalDetails": "The vulnerability in CAYIN CMS-WS, CMS-SE, and SMP series products manifests as a failure in the application's file upload handling mechanism, which lacks adequate sanitization or verification of file types and extensions.\nRoot cause analysis indicates that the server-side logic fails to enforce strict allow-listing of file types or properly validate the MIME type and content headers of uploaded files. This oversight allows an attacker to bypass existing security filters and upload executable script files, such as PHP, JSP, or ASPX web shells, into web-accessible directories.\nThe attack flow commences with the attacker authenticated as an administrative or privileged user. The attacker identifies a legitimate administrative interface or file management module within the CAYIN product intended for administrative configuration or asset management. By intercepting the request or interacting directly with the upload function, the attacker submits a specially crafted payload—a web shell designed to facilitate remote command execution.\nOnce the file is successfully uploaded to the target directory, the attacker performs a direct HTTP GET request to the file path of the uploaded script. The web server interprets and executes the malicious code, granting the attacker a persistent entry point to the operating system.\nPost-exploitation behavior typically involves the execution of system-level commands, allowing the attacker to probe the internal network, exfiltrate sensitive configuration files, or install further backdoors to ensure persistent access. Since the web server process is often executed with elevated permissions, the resulting command execution often grants the attacker broad control over the underlying Linux or Windows server environment.\nThe vulnerability is inherent to the product architecture within the specified CMS-WS, CMS-SE, and SMP series, emphasizing the need for robust input validation and restricted execution policies for any user-writable directory on the server."
}