CVE-2026-18671 in IBM
Summary
by MITRE • 08/13/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow an authenticated attacker to force a NetServer server thread exception, caused by an integer overflow during bounds checking in request processing. The attacker could exploit this vulnerability to cause a temporary denial of service.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 08/13/2026
This vulnerability affects IBM i operating systems version 7.6, 7.5, 7.4, and 7.3, specifically targeting the NetServer component that handles network services. The flaw manifests as an integer overflow condition during bounds checking operations within request processing mechanisms, representing a critical security weakness that could be exploited by authenticated attackers to disrupt system availability. The vulnerability stems from improper validation of input parameters when processing network requests, where integer arithmetic operations exceed their defined limits and cause unexpected behavior in the server thread management system.
The technical implementation of this vulnerability involves the NetServer service maintaining server threads to handle incoming network connections and requests. When an attacker submits a crafted request with malformed parameters that trigger integer overflow conditions during bounds checking, the system's memory management routines encounter unexpected values that can lead to thread exceptions or crashes. This specific flaw falls under CWE-190, which describes integer overflow conditions, while also aligning with CWE-129, representing improper validation of array indices and buffer limits. The overflow occurs during request processing where integer variables used for bounds checking exceed their maximum representable values, causing the system to behave unpredictably.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by authenticated attackers to repeatedly disrupt critical network services provided by IBM i systems. The temporary denial of service affects NetServer functionality, potentially impacting database connectivity, file sharing, and other network-based applications that rely on these services. Attackers with valid credentials can exploit this weakness systematically, causing server threads to crash or become unresponsive, which may require manual intervention to restore normal operations. This vulnerability particularly affects enterprise environments where IBM i systems serve as backend servers for critical business applications and data services.
Organizations should implement immediate mitigations including applying the latest security patches from IBM that address the integer overflow condition in NetServer thread management. System administrators should also consider implementing network segmentation to limit access to NetServer services, thereby reducing the attack surface available to authenticated users who might exploit this vulnerability. Monitoring solutions should be configured to detect unusual patterns in server thread behavior or frequent restarts of NetServer processes, which could indicate exploitation attempts. Additionally, implementing proper input validation controls and rate limiting for network requests can help reduce the likelihood of successful exploitation while maintaining system availability for legitimate users.
The vulnerability demonstrates how seemingly minor flaws in input validation can result in significant operational disruptions in enterprise systems, emphasizing the importance of comprehensive security testing and regular patch management procedures. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving denial of service attacks and privilege escalation through authenticated access points, making it particularly concerning for environments where multiple users have legitimate access to IBM i systems. Organizations should also conduct thorough risk assessments to determine the potential impact on their specific configurations and implement additional defensive measures such as intrusion detection systems and regular security audits to prevent exploitation attempts.