CVE-2026-18250: IBM i Privilege Escalation Vulnerability

CVE-2026-18250 Overview

CVE-2026-18250 is a race condition vulnerability affecting IBM i versions 7.6, 7.5, 7.4, and 7.3. A remote authenticated attacker can exploit the flaw to obtain sensitive information and bypass security restrictions on affected systems. The issue is classified under [CWE-362] Concurrent Execution using Shared Resource with Improper Synchronization.

The vulnerability requires valid authentication credentials and network access to the target IBM i system. Successful exploitation compromises confidentiality, integrity, and availability at a limited scope. IBM has published a support advisory addressing the flaw.

Critical Impact
Authenticated remote attackers can win a race condition on IBM i to disclose sensitive data and bypass security controls across multiple supported releases.

Affected Products

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

Discovery Timeline

2026-08-12 - CVE-2026-18250 published to NVD
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-18250

Vulnerability Analysis

The vulnerability stems from a race condition [CWE-362] in IBM i where concurrent operations access a shared resource without proper synchronization. An attacker with valid credentials can trigger simultaneous requests that create a timing window between security state checks and resource use. Winning this window allows the attacker to read data or perform actions that would otherwise be blocked.

Because the flaw impacts confidentiality, integrity, and availability at a limited level, exploitation can yield fragments of sensitive information and enable partial bypass of enforcement logic. The bug affects four supported IBM i releases, indicating the defective code path exists in shared operating system components rather than a release-specific feature.

Root Cause

The root cause is improper synchronization during concurrent execution. Security-relevant checks and the subsequent use of the protected resource are not performed atomically. This time-of-check to time-of-use (TOCTOU) style gap lets a second thread modify state after validation but before enforcement completes.

Attack Vector

Exploitation requires network reachability to the IBM i service and valid low-privilege credentials. The attacker issues concurrent requests designed to interleave with a privileged code path. No user interaction is required. Refer to the IBM Support Article for vendor technical details.

Detection Methods for CVE-2026-18250

Indicators of Compromise

Unusual bursts of concurrent authenticated requests from a single user or IP against IBM i services.
Audit journal entries showing access to sensitive objects immediately following rapid repeated permission checks.
Access patterns where a user retrieves data outside their normal authority scope during periods of high request concurrency.

Detection Strategies

Enable and centralize IBM i audit journal (QAUDJRN) collection with focus on *AUTFAIL, *OBJMGT, and *SECURITY audit values.
Baseline per-user request rates and alert on statistical anomalies indicative of race-condition exploitation attempts.
Correlate authentication events with object access events to surface sequences that suggest bypassed authority checks.

Monitoring Recommendations

Forward IBM i security audit data to a SIEM for long-term retention and cross-source correlation.
Monitor privileged profile activity (*ALLOBJ, *SECADM) for unexpected escalation or data access following bulk request activity.
Track outbound data volumes from IBM i partitions to detect exfiltration that follows successful exploitation.

How to Mitigate CVE-2026-18250

Immediate Actions Required

Apply the IBM PTFs referenced in the vendor advisory for IBM i 7.6, 7.5, 7.4, and 7.3 as soon as they are available for your release.
Restrict network access to IBM i services so only trusted management networks can reach affected interfaces.
Review and reduce user authorities, ensuring least privilege for all interactive and program-based profiles.

Patch Information

IBM provides remediation guidance in the IBM Support Article. Administrators should identify the applicable Group PTF level for each installed release and schedule installation during the next maintenance window.

Workarounds

Limit the number of concurrent sessions per user profile to reduce the exploitability of the race window.
Enforce network segmentation and firewall rules so IBM i services are unreachable from untrusted zones.
Increase audit logging depth on sensitive objects to detect exploitation attempts until patches are applied.

bash

# Configuration example: tighten IBM i auditing and session limits
CHGSYSVAL SYSVAL(QAUDCTL) VALUE('*AUDLVL *OBJAUD')
CHGSYSVAL SYSVAL(QAUDLVL) VALUE('*AUTFAIL *SECURITY *OBJMGT')
CHGUSRPRF USRPRF(TARGETUSER) MAXSTG(*NOMAX) LMTDEVSSN(*YES)