CVE-2026-19086 in IBM
Summary
by MITRE • 09/15/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a denial of service as a result of a buffer overflow in a PASE process. An authenticated attacker could leverage this to terminate their own process.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified within IBM i operating system versions 7.6, 7.5, 7.4, and 7.3 represents a critical memory management flaw located specifically within the Portable Application Solutions Environment or PASE subsystem. This environment serves as a compatibility layer that allows Unix-based applications to run on the IBM i platform, bridging the gap between traditional AS/400 architecture and standard POSIX-compliant software ecosystems. The core technical defect is classified as a buffer overflow, which occurs when an application writes more data to a fixed-length block of memory than it can hold. In this specific context, the flaw resides within the PASE process handling logic, where insufficient bounds checking allows external inputs or internal operations to overwrite adjacent memory locations. This overwriting corrupts the control flow of the program execution, leading directly to an abnormal termination of the affected process rather than allowing for graceful error handling or secure failure modes.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-120, which denotes Buffer Copy without Checking Size of Input. The mechanism relies on the attacker providing crafted input that exceeds the allocated buffer size defined by the PASE subsystem's internal structures. Because IBM i utilizes an integrated security model where users operate within specific job environments and authority levels, the exploitation vector requires authentication. An authenticated user must be able to interact with a vulnerable service or application running under their own credentials to trigger the overflow condition. Once triggered, the memory corruption causes the operating system kernel or the PASE runtime environment to detect an illegal operation, resulting in the immediate termination of the process. This behavior is consistent with CWE-400, which describes Uncontrolled Resource Consumption leading to Denial of Service conditions within a specific context.
The operational impact of this vulnerability is primarily confined to availability rather than confidentiality or integrity at the system-wide level. Since the attacker can only terminate their own process, the immediate effect is a denial of service for that specific user session and any applications running under it. While this may not cause a complete outage of the entire IBM i partition, it disrupts business continuity for individual users who rely on continuous processing capabilities within PASE environments. For organizations utilizing long-running background jobs or critical batch processes managed through PASE, such abrupt terminations can lead to data inconsistency if transactions are not properly rolled back by higher-level application logic. Furthermore, repeated exploitation attempts could contribute to resource exhaustion if the system is configured to automatically restart terminated services without adequate rate limiting or monitoring thresholds in place.
In terms of threat modeling and adversary behavior, this vulnerability maps directly to MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically under the sub-technique for application crash exploitation. The attacker leverages a known weakness in software implementation to disrupt service availability without needing elevated privileges or lateral movement capabilities initially. This makes it particularly relevant for insider threats or compromised accounts where an adversary seeks to degrade system performance or distract security teams by generating noise through repeated process terminations. It does not currently indicate privilege escalation vectors, meaning the attacker cannot directly gain control over other users' processes or the underlying operating system kernel from this specific flaw alone.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is to apply the latest security patches provided by IBM for all affected versions of IBM i 7.3 through 7.6. These updates typically include fixes that enforce stricter memory boundary checks within the PASE subsystem, preventing the buffer overflow from occurring in the first place. Organizations should prioritize patching systems where authenticated users have direct access to interactive shells or web-facing applications running on PASE. Additionally, implementing strict input validation at the application layer for any custom code deployed within the PASE environment can provide defense-in-depth against similar memory corruption issues. Monitoring tools should be configured to alert on frequent process terminations associated with specific user IDs, allowing security operations centers to detect potential exploitation attempts and isolate affected accounts before significant operational disruption occurs.