CVE-2026-18318 in IBM
Summary
by MITRE • 10/13/2026
IBM i 7.3, 7.4, 7.5, and 7.6 could allow a remote attacker to perform brute-force attacks to obtain credentials due to improper authentication.
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Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified in IBM i operating system versions 7.3 through 7.6 represents a critical security flaw rooted in the subsystem's handling of authentication mechanisms for network services. This defect allows an unauthenticated, remote attacker to exploit weaknesses in how credentials are validated during login attempts. Unlike vulnerabilities that require specific configuration errors or privileged access to trigger, this issue stems from fundamental logic flaws within the authentication protocol implementation itself. The core technical flaw involves insufficient rate limiting and lack of account lockout policies by default for certain network-facing services exposed on IBM i systems. When a remote client initiates an authentication sequence against these vulnerable components, the system does not adequately restrict the number of consecutive failed login attempts or implement effective delays between successive connection requests. This absence of robust throttling mechanisms creates a permissive environment where automated tools can rapidly cycle through large volumes of potential username and password combinations without triggering defensive countermeasures such as temporary account suspension or progressive delay penalties.
From an operational perspective, this vulnerability significantly lowers the barrier for entry for malicious actors seeking to compromise system integrity. By leveraging brute-force attack techniques, adversaries can systematically guess valid credentials across multiple accounts hosted on the affected IBM i instances. The impact extends beyond simple unauthorized access; successful exploitation can lead to full system takeover, allowing attackers to execute arbitrary commands, exfiltrate sensitive data, install persistent backdoors, or pivot further into connected network segments. Given that IBM i is often deployed in enterprise environments handling critical business operations and financial transactions, the compromise of even a single instance can have cascading effects on organizational availability, confidentiality, and integrity. The ease with which automated scripts can exploit this flaw means that systems exposed to untrusted networks are at constant risk of being compromised through high-volume credential stuffing or dictionary attacks targeting common default passwords or weakly configured user accounts.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) category CWE-307, which describes Improper Restriction of Excessive Authentication Attempts. It also maps to the MITRE ATT&CK framework under technique T1110, specifically subtechnique T1110.001 for Brute Force attacks. The lack of effective rate limiting and account lockout mechanisms is a classic indicator of this attack vector being viable against the target system. Security researchers emphasize that while brute-force attacks are well-known, their effectiveness increases dramatically when systems fail to implement basic defensive controls designed to detect and mitigate such behavior over time.
To mitigate this risk, organizations running IBM i 7.3 through 7.6 must immediately apply vendor-provided security patches or updates that address the authentication logic flaws. In addition to applying fixes, administrators should enforce strict account lockout policies within the operating system's security settings to limit the number of failed login attempts before an account is temporarily disabled. Implementing network-level controls such as firewalls and intrusion prevention systems can further reduce exposure by restricting access to IBM i services only from trusted IP addresses or subnets. Enabling multi-factor authentication where supported adds a critical layer of defense that renders stolen credentials useless without the second factor. Regular auditing of login attempts and monitoring for anomalous patterns, such as high volumes of failed authentications from single sources, can help detect ongoing brute-force campaigns early. Ultimately, securing IBM i environments requires a combination of timely patching, rigorous configuration hardening, and continuous monitoring to counteract exploitation attempts targeting authentication weaknesses.