CVE-2026-17109: IBM i Parameter Injection Vulnerability

CVE-2026-17109 Overview

CVE-2026-17109 is a parameter injection vulnerability affecting IBM i versions 7.6, 7.5, 7.4, and 7.3. A remote authenticated attacker can add unexpected parameters to a command, potentially altering its intended behavior. The flaw is classified under [CWE-20: Improper Input Validation] and requires valid credentials plus network access to exploit. Successful exploitation impacts availability but does not directly expose data or allow code execution.

Critical Impact
Authenticated attackers can inject unexpected command parameters against IBM i systems, disrupting command execution and affecting availability of business-critical workloads.

Affected Products

IBM i 7.6
IBM i 7.5
IBM i 7.4
IBM i 7.3

Discovery Timeline

2026-08-12 - CVE CVE-2026-17109 published to NVD
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-17109

Vulnerability Analysis

The vulnerability stems from improper input validation in the way IBM i processes command parameters. An authenticated user with low privileges can append or inject additional parameters that the command interpreter accepts without adequate sanitization. This alters the command's runtime behavior in ways the invoking application or administrator did not intend.

Because exploitation requires authentication and yields no confidentiality or integrity impact, the practical risk centers on availability. Injected parameters can cause commands to abort, consume resources, or reach unintended execution paths that terminate dependent processes. Enterprises running long-lived IBM i workloads for finance, ERP, and supply-chain functions face operational disruption if the flaw is triggered against production commands.

Root Cause

The root cause is missing or insufficient validation of parameter boundaries when commands are constructed from user-influenced input. Under [CWE-20], the affected command handling accepts additional tokens beyond the expected parameter set. The interpreter then acts on those tokens rather than rejecting the malformed invocation.

Attack Vector

Exploitation occurs over the network and requires valid authentication to the IBM i system. An attacker with an existing user profile submits a crafted command that appends unexpected parameters, causing the target command to behave in ways outside its documented specification. No user interaction is required to complete the attack. Refer to the IBM Support Page for vendor-specific technical detail.

Detection Methods for CVE-2026-17109

Indicators of Compromise

Command history entries showing unexpected or malformed parameter combinations submitted by low-privilege user profiles.
Job logs on IBM i containing abnormal termination messages tied to commands invoked with extra tokens.
Repeated failed command invocations from a single authenticated session targeting administrative CL commands.

Detection Strategies

Enable IBM i audit journal (QAUDJRN) entries for command execution (CD audit type) and review for parameter anomalies.
Correlate authenticated user session activity with command syntax deviations across production LPARs.
Baseline normal command usage per user profile and alert on statistical outliers in parameter count or content.

Monitoring Recommendations

Forward IBM i audit journal data to a centralized analytics platform for cross-system correlation.
Monitor for privilege changes or profile creation events preceding suspicious command activity.
Track availability metrics of IBM i subsystems to detect service interruptions consistent with command disruption.

How to Mitigate CVE-2026-17109

Immediate Actions Required

Apply the IBM-supplied PTF referenced on the IBM Support Page for each affected release (7.3, 7.4, 7.5, 7.6).
Review and reduce the number of user profiles with command-line access using LMTCPB(*YES) where feasible.
Rotate credentials for any accounts showing anomalous command activity in the audit journal.

Patch Information

IBM has published guidance and fix availability on its support portal. Administrators should consult the IBM Support Page to identify the correct PTF or group PTF for their installed release and apply it through standard IBM i maintenance procedures.

Workarounds

Restrict command-line capability on user profiles that do not require it by setting LMTCPB(*YES).
Enforce least-privilege authority on sensitive CL commands using GRTOBJAUT and RVKOBJAUT to limit invocation.
Require multi-factor authentication for interactive IBM i sessions to raise the barrier to authenticated exploitation.

bash

# Configuration example: restrict command capability for a user profile
CHGUSRPRF USRPRF(APPUSER) LMTCPB(*YES)

# Revoke public authority on a sensitive command
RVKOBJAUT OBJ(QSYS/SBMJOB) OBJTYPE(*CMD) USER(*PUBLIC) AUT(*ALL)
GRTOBJAUT OBJ(QSYS/SBMJOB) OBJTYPE(*CMD) USER(OPERATOR) AUT(*USE)