CVE-2026-17469 in IBM
Summary
by MITRE • 09/04/2026
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a local authenticated attacker to cause a denial of service due to an off-by-one write in the LPD queue name parser.
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Analysis
by VulDB Data Team • 09/05/2026
The vulnerability identified involves a critical memory corruption flaw within the Line Printer Daemon (LPD) subsystem of IBM i operating systems, specifically affecting versions 7.3 through 7.6. This issue stems from an improper boundary check during the parsing of LPD queue names, resulting in an off-by-one write error. In software development, such errors occur when a loop or array access operation exceeds its intended bounds by exactly one unit, often due to incorrect index calculations or missing validation checks for null terminators and string lengths. When an attacker provides a specifically crafted input string as part of the LPD queue name parameter, the parser fails to correctly account for the memory required to store the processed data, leading to a write operation that overwrites adjacent memory locations on the stack or heap.
From a technical perspective, this flaw represents a classic buffer overflow condition classified under CWE-193: Off-by-One Error. The LPD service is responsible for handling print requests and managing printer queues within the IBM i environment. Because the vulnerability resides in the name parsing logic, it requires an attacker to interact with the LPD interface directly. This interaction typically involves sending a maliciously formatted request that triggers the flawed parser routine. The resulting memory corruption can lead to unpredictable system behavior, including application crashes or data integrity issues depending on what critical structures reside adjacent to the affected buffer in memory.
The primary operational impact of this vulnerability is a denial of service against the LPD subsystem and potentially the broader operating system if the crash propagates beyond the immediate process context. A local authenticated attacker can exploit this flaw by repeatedly sending crafted requests, causing the LPD daemon or associated worker processes to terminate unexpectedly. This disruption prevents legitimate users from submitting print jobs and may require administrative intervention to restart services or reboot systems if kernel-level stability is compromised. While the vulnerability does not inherently allow for arbitrary code execution without further exploitation techniques such as return-oriented programming, its reliability in causing service interruption makes it a significant threat to system availability.
This incident aligns with MITRE ATT&CK technique T1499: Endpoint Denial of Service, specifically under sub-techniques involving resource exhaustion or application crashes via memory corruption. The attack vector is classified as Local because the attacker must have valid authentication credentials and direct access to the IBM i system before they can interact with the LPD service. This constraint limits the scope of potential adversaries but does not diminish the severity for internal threats, such as disgruntled employees or compromised user accounts that gain local shell access.
Mitigation strategies should focus on both immediate remediation and long-term hardening practices. The most effective solution is to apply the latest security patches provided by IBM, which address the boundary checks within the LPD queue name parser. Administrators should verify their system versions against the affected list of 7.3 through 7.6 and ensure that all interim fixes are installed promptly. Additionally, implementing strict input validation at the application layer can provide defense-in-depth, although patching remains the primary corrective action. Network segmentation policies should also be reviewed to restrict access to LPD services only from trusted print servers or management stations, reducing the attack surface available to potential local attackers who might attempt lateral movement after initial compromise.