CVE-2026-18235 Overview
CVE-2026-18235 is a command injection vulnerability affecting IBM i versions 7.6, 7.5, 7.4, and 7.3. The flaw stems from insufficient input validation, allowing a remote authenticated attacker to execute arbitrary Control Language (CL) commands on the target system. The vulnerability is classified under [CWE-78] (Improper Neutralization of Special Elements used in an OS Command).
Successful exploitation can compromise system confidentiality and integrity, with limited impact to availability. IBM published an advisory on the IBM Support Page detailing affected releases and remediation guidance.
Critical Impact
A low-privileged remote attacker can execute arbitrary CL commands on IBM i systems, gaining unauthorized access to sensitive data and system functions.
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-2026-18235 published to NVD
- 2026-08-12 - Last updated in NVD database
Technical Details for CVE-2026-18235
Vulnerability Analysis
The vulnerability resides in an IBM i component that accepts user-supplied input and passes it to the Control Language (CL) command interpreter without adequate sanitization. An authenticated attacker with network access can craft input containing CL command separators or embedded commands. When the affected component processes the input, the injected commands execute in the context of the underlying service.
CL is the primary scripting and administration language on IBM i. Command execution through CL provides direct access to system objects, libraries, user profiles, and integrated file system paths. This makes command injection on IBM i functionally equivalent to shell injection on Unix-like systems.
Exploitation requires valid credentials but no user interaction. The attack can be launched remotely over the network, and its low complexity increases the risk of automated exploitation against exposed IBM i services.
Root Cause
The root cause is improper neutralization of special elements used in an OS command, mapped to [CWE-78]. The affected code path constructs a CL command string using attacker-controlled input without escaping, quoting, or restricting metacharacters. This allows an attacker to break out of the intended command context and append arbitrary CL statements.
Attack Vector
The attack vector is network-based and requires low privileges. An authenticated attacker submits a specially crafted request to an IBM i service that ultimately invokes a CL command using the tainted input. Because CL commands run with the privileges of the invoking process, the attacker inherits those permissions and can enumerate objects, read data, or modify system configuration.
No exploit code is publicly available at the time of publication, and the vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog. Refer to the IBM Support Page for technical remediation details.
Detection Methods for CVE-2026-18235
Indicators of Compromise
- Unexpected CL command execution originating from service accounts or interactive jobs not typically associated with administrative activity.
- Anomalous entries in the QHST system history log and QAUDJRN audit journal referencing sensitive commands such as CRTUSRPRF, CHGUSRPRF, or RUNRMTCMD.
- Network traffic from unusual sources to IBM i services followed by new job initiations under low-privilege user profiles.
Detection Strategies
- Enable and monitor the IBM i security audit journal (QAUDJRN) for command-string (CD) and object-access (ZC, ZR) audit entries tied to affected services.
- Correlate authentication events with subsequent CL command execution to identify low-privilege accounts running administrative commands.
- Deploy file integrity monitoring on IBM i libraries containing sensitive user profiles, job descriptions, and exit programs.
Monitoring Recommendations
- Forward IBM i audit journal data to a centralized analytics platform for behavioral baselining and alerting.
- Alert on CL commands executed outside approved change windows or by non-administrative profiles.
- Track failed and successful authentication attempts against IBM i network services to identify credential stuffing that could precede exploitation.
How to Mitigate CVE-2026-18235
Immediate Actions Required
- Apply the IBM PTFs referenced in the IBM Support Page for IBM i 7.6, 7.5, 7.4, and 7.3.
- Inventory all IBM i systems and confirm the current PTF level to prioritize patching of internet-exposed or business-critical hosts.
- Rotate credentials for any user profiles that may have been exposed to untrusted networks.
Patch Information
IBM has published remediation guidance and Program Temporary Fixes (PTFs) for the affected IBM i releases. Administrators should consult the IBM Support Page for the specific PTF identifiers and installation procedures corresponding to each supported release.
Workarounds
- Restrict network access to IBM i host services using firewalls and IBM i exit programs, limiting connections to trusted management subnets.
- Enforce least-privilege user profiles by removing unnecessary special authorities such as *ALLOBJ, *SECADM, and *JOBCTL from application accounts.
- Require strong authentication and monitor for anomalous authentication patterns until patches are applied.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
