Description

NUMail developed by Green-Computing has an OS Command Injection vulnerability. Unauthenticated remote attackers can inject arbitrary OS commands and execute them on the server.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-08-28T05:16:47.083Z",
  "pubdate": "2026-08-28T05:16:47.083Z",
  "executiveSummary": "NUMail, developed by Green-Computing, contains a critical OS command injection vulnerability. This security flaw allows unauthenticated remote attackers to execute arbitrary system-level commands on the underlying server hosting the application. The vulnerability stems from improper neutralization of user-supplied input before passing it to a system shell or executive function. By leveraging this flaw, an attacker can bypass standard application authentication and gain unauthorized control over the server environment. The impact of this vulnerability is severe, potentially resulting in a complete system compromise, including unauthorized data access, lateral movement within the network, and the deployment of persistent malicious software. There are no authentication requirements for exploitation, significantly lowering the barrier for entry for malicious actors. Organizations utilizing NUMail are at high risk, as the vulnerability resides at the application layer, directly exposing the host operating system to external manipulation. Remediation is necessary to prevent remote code execution and maintain the integrity and confidentiality of the server infrastructure.",
  "technicalDetails": "The vulnerability in NUMail is characterized as an OS Command Injection flaw. This occurs when the application constructs system commands using unsanitized user-provided input, allowing an attacker to escape the intended command context and inject arbitrary malicious payloads.\nThe root cause is identified as the application's failure to perform adequate input validation or parameterization when interacting with the host operating system's command shell (e.g., /bin/sh or cmd.exe). When the application executes functions that spawn child processes, it inadvertently trusts external input as part of the command string.\nExploitation is possible without prior authentication. An attacker can craft a request containing shell metacharacters—such as semicolons, pipes, ampersands, or backticks—to chain their own commands to the legitimate process. For example, if the application invokes a system utility to process a user-defined parameter, the attacker can submit a payload structured to terminate the initial command and initiate a secondary command, such as retrieving a remote reverse shell script or performing unauthorized file system manipulation.\nThe attack flow proceeds as follows: First, the attacker identifies an input vector within the NUMail interface that interacts with server-side processing. Second, the attacker submits a specially crafted string designed to manipulate the underlying command syntax. Third, the server interprets this string as a series of instructions, executing the injected commands with the privileges of the application's service account. Finally, the attacker achieves remote code execution, granting them the ability to inspect sensitive configuration files, exfiltrate data, or install persistent backdoors.\nThis vulnerability leads to full system compromise. Because the injected commands execute with the application's process permissions, the scope of the impact is determined by the service account's privileges. If the application is running as root or a highly privileged user, the attacker inherits those capabilities, enabling them to disable security logging, alter system binaries, or pivot into other internal network segments. This exposure is particularly critical given the lack of authentication, as any remote entity capable of reaching the NUMail service can trigger this payload behavior, leading to uncontrolled command execution on the host server."
}