CVE-2026-17273 in IBM
Summary
by MITRE • 09/04/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote authenticated attacker to cause a denial of service due to a NULL pointer dereference.
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Analysis
by VulDB Data Team • 09/04/2026
The vulnerability identified in IBM i operating system versions 7.6, 7.5, 7.4, and 7.3 represents a critical reliability issue stemming from improper handling of memory pointers within the application logic. This flaw allows a remote authenticated attacker to trigger a denial of service condition by exploiting a NULL pointer dereference error. In software engineering terms, this occurs when an application attempts to access or modify data at a memory address that is null rather than pointing to valid allocated memory. Such errors typically arise from insufficient validation checks before accessing pointers returned by system calls or internal functions, particularly in scenarios where expected inputs are missing, malformed, or unexpectedly empty. The presence of authentication requirements indicates that the attacker must possess valid credentials for an account on the affected IBM i system, which limits the attack surface to insider threats or compromised user accounts but does not mitigate the severity of the resulting impact once access is gained.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-476, which describes NULL Pointer Dereference as a weakness where an application dereferences a pointer that it expects to be valid but is actually null. When such a condition occurs in a server-side process or service running on IBM i, the operating system typically terminates the affected process immediately to prevent further corruption of memory space. In the context of enterprise infrastructure services hosted on these versions of IBM i, this abrupt termination can lead to significant operational disruptions. If the vulnerable component is part of a critical business application or a core system service, its failure may render associated applications unavailable, interrupt batch processing jobs, or cause session drops for legitimate users relying on those specific functionalities. The impact extends beyond simple downtime; it introduces unpredictability into system stability and can necessitate manual intervention by administrators to restart services, thereby increasing operational overhead and potential data inconsistency risks if transactions were in progress at the time of failure.
The exploitation vector is classified under MITRE ATT&CK technique T1499, specifically Endpoint Denial of Service, as it involves exhausting or disrupting resources through a targeted action rather than overwhelming them with volume like a DDoS attack. Because authentication is required, this vulnerability falls into the category of insider threats or lateral movement scenarios where an attacker has already breached perimeter defenses and obtained user privileges. The lack of proper input validation suggests that developers did not adequately account for edge cases in API endpoints or internal function calls that process external data inputs. This oversight highlights a gap in secure coding practices regarding defensive programming, specifically the failure to verify pointer validity before use. Such gaps are often found in legacy codebases where rapid development cycles may have bypassed rigorous static analysis or penetration testing phases designed to catch low-level memory management errors.
Mitigation strategies for this vulnerability primarily involve applying vendor-supplied patches that address the underlying code defect by adding necessary null checks and error handling routines before pointer dereference operations occur. Organizations running IBM i 7.3 through 7.6 should prioritize updating their systems using official security fixes released by IBM to resolve these specific memory management issues. In addition to patching, implementing strict access controls is essential to minimize the risk of exploitation. This includes enforcing multi-factor authentication for all administrative and privileged accounts, regularly auditing user permissions to ensure least privilege principles are applied, and monitoring system logs for unusual patterns such as frequent service restarts or unexpected process terminations that might indicate attempted exploitation attempts. Furthermore, deploying intrusion detection systems capable of analyzing application-level behavior can help identify anomalous requests from authenticated users that trigger these vulnerabilities before they cause sustained outages. Regular vulnerability assessments focused on input validation flaws will also aid in identifying similar weaknesses across the environment proactively.