Description

IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local authenticated attacker to inject parameters into a CL command due to improper neutralization of special elements.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.4",
  "pubDate": "2026-09-04T17:16:55.627Z",
  "pubdate": "2026-09-04T17:16:55.627Z",
  "executiveSummary": "A security vulnerability has been identified in IBM i operating system versions 7.6, 7.5, 7.4, and 7.3, which allows a local authenticated attacker to inject parameters into Control Language (CL) commands.\nThis flaw is classified under improper neutralization of special elements within command inputs, commonly referred to as command injection. An attacker possessing valid local credentials can exploit this weakness by supplying specifically crafted inputs containing control characters or delimiters to applications that dynamically construct and execute CL commands. If the application fails to properly sanitize or validate these inputs before execution, the command interpreter processes the injected parameters as part of the intended command structure.\nThe impact of successful exploitation includes unauthorized privilege escalation, access to sensitive system resources, modification of critical system configuration files, or arbitrary code execution under the security context of the vulnerable application. Since the vulnerability requires local authentication, the exposure is restricted to users with direct system access, but it represents a significant elevation of risk in multi-tenant or shared environments.",
  "technicalDetails": "Control Language (CL) is the primary command-line interface and scripting language utilized within the IBM i operating system environment. Applications running on IBM i often programmatically execute CL commands using system APIs (such as QCMDEXC) or built-in functions to perform administrative tasks, manage files, or control job execution. The vulnerability arises when an application dynamically concatenates user-supplied input into a CL command string without neutralizing special characters or delimiters.\nIn the IBM i environment, CL commands utilize specific delimiters, such as single quotes for string literals and spaces to separate parameters. If an application accepts input from a local authenticated user and embeds it directly into a command string, the attacker can manipulate the command's structure. By introducing delimiters like single quotes or parentheses, the attacker can close the intended parameter prematurely and append additional parameters or commands.\nThe attack flow typically begins with a local authenticated user identifying an application interface or system utility that accepts parameter inputs. The attacker inputs a crafted payload containing special characters designed to break out of the input field context. When the application passes this payload to the command execution interface (e.g., QCMDEXC), the interpreter parses the injected characters as syntax rather than literal data. This allows the attacker to execute unauthorized parameters, modify command behavior, or run secondary commands in the context of the calling program.\nThe technical impact is heavily dependent on the privileges of the user profile running the vulnerable application. If the application executes with elevated privileges (such as *ALLOBJ or *SECADM authorities), the injected parameters will run with those same high privileges. This can lead to complete compromise of the logical partition (LPAR), unauthorized access to DB2 databases, or modification of system security configurations. The root cause is the lack of strict input sanitization, parameter validation, or safe API usage when building command strings dynamically.\nTo mitigate this risk at the code level, developers should avoid dynamic command concatenation. Instead, utilizing strongly typed APIs or parameter-passing interfaces that do not invoke the command interpreter's parsing engine prevents the interpretation of user input as command syntax. In IBM i, this means avoiding the construction of raw command strings for QCMDEXC when safer programming practices, such as parameter binding or dedicated system APIs, are available. Additionally, implementing strict allow-lists for inputs and escaping control characters are essential defensive measures when dynamic execution cannot be avoided."
}