CVE-2026-18078 Overview
CVE-2026-18078 is an integer overflow vulnerability [CWE-190] affecting IBM i versions 7.3, 7.4, 7.5, and 7.6. A remote authenticated attacker can trigger the condition to cause a denial of service on the affected system. The flaw impacts availability but does not compromise confidentiality or integrity. IBM has published a security bulletin describing the affected releases and remediation guidance.
Critical Impact
Authenticated remote attackers can crash or destabilize IBM i services across supported releases 7.3 through 7.6, disrupting business-critical workloads hosted on the platform.
Affected Products
- IBM i 7.3
- IBM i 7.4
- IBM i 7.5 and 7.6
Discovery Timeline
- 2026-09-04 - CVE-2026-18078 published to the National Vulnerability Database
- 2026-09-08 - Last updated in NVD database
Technical Details for CVE-2026-18078
Vulnerability Analysis
The vulnerability is an integer overflow condition in IBM i that an authenticated remote user can trigger over the network. When the overflow occurs, the affected component fails to handle the resulting value correctly, leading to a denial of service. The issue affects all currently supported IBM i releases: 7.3, 7.4, 7.5, and 7.6.
Because exploitation requires valid credentials, the attack surface is limited to users who already have authenticated access to the system. The EPSS model currently estimates a low probability of exploitation in the near term, and no public proof-of-concept has been observed. Refer to the IBM Support Documentation for the full advisory.
Root Cause
The root cause is an integer overflow [CWE-190] in an IBM i component that processes attacker-influenced numeric input. When the calculated value exceeds the storage bounds of its integer type, it wraps or truncates, driving the affected service into an inconsistent state that results in a crash.
Attack Vector
Exploitation is remote and network-based but requires prior authentication with low privileges. No user interaction is needed. A successful request causes high availability impact on the targeted IBM i partition or service. IBM's advisory does not disclose exploit details, and no public proof-of-concept code is available at this time.
See the IBM Support Documentation for exact affected components and patch identifiers.
Detection Methods for CVE-2026-18078
Indicators of Compromise
- Unexpected termination or restart of IBM i services or subsystems handling network requests.
- Repeated abnormal disconnects tied to a specific authenticated user session.
- System operator messages indicating exception handling or resource errors correlated with inbound network activity.
Detection Strategies
- Correlate IBM i job logs (QSYSOPR, QHST) with network authentication events to identify sessions preceding service failures.
- Monitor for abnormal termination messages and function-check exceptions on affected releases 7.3 through 7.6.
- Baseline normal request patterns to authenticated network services and alert on anomalous payload sizes or malformed inputs.
Monitoring Recommendations
- Forward IBM i audit journal (QAUDJRN) entries and system history logs to a centralized SIEM for correlation.
- Track authentication events and session origins for accounts with network access to IBM i partitions.
- Alert on repeated service restarts or availability drops on IBM i hosts following authenticated network activity.
How to Mitigate CVE-2026-18078
Immediate Actions Required
- Review the IBM Support Documentation and apply the PTFs listed for your IBM i release.
- Inventory all IBM i systems running versions 7.3, 7.4, 7.5, and 7.6 and prioritize patching internet-exposed or multi-tenant partitions.
- Audit user accounts with network access and remove or restrict unnecessary privileges.
Patch Information
IBM has published remediation guidance in the vendor advisory. Administrators should apply the Program Temporary Fixes (PTFs) referenced in the IBM Support Documentation for each affected release. Confirm the PTF level after installation using standard IBM i commands such as DSPPTF.
Workarounds
- Restrict network access to IBM i services using exit programs, firewall rules, or IP filtering until PTFs are applied.
- Enforce least privilege on user profiles and disable unused authenticated network services.
- Monitor and rate-limit authenticated sessions to reduce the ability of a single account to trigger the overflow repeatedly.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
