CVE-2026-89859 in Linux
Summary
by MITRE • 09/16/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: qla2xxx: Zero dport diagnostics buffer to avoid info leak
qla2x00_do_dport_diagnostics() allocates the qla_dport_diag response buffer with kmalloc_obj() (non-zeroing) and, on success, copies the full sizeof(*dd) back to user space via sg_copy_from_buffer(). The inbound sg_copy_to_buffer() only fills as many bytes as the user request payload provides, and qla26xx_dport_diagnostics() zeroes only dd->buf. The options and unused[] fields are therefore copied out uninitialized,
leaking kernel heap contents to user space.
Allocate with kzalloc_obj(), matching qla2x00_do_dport_diagnostics_v2().
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Analysis
by VulDB Data Team • 09/16/2026
The Linux kernel driver for QLogic Fibre Channel adapters contains a critical information disclosure vulnerability within the scsi_qla2xxx subsystem, specifically in the function responsible for handling diagnostic port operations. This flaw arises from improper memory initialization practices when allocating buffers for user-space communication. The core issue lies in the use of kmalloc_obj() to allocate the qla_dport_diag response buffer. Unlike its counterpart kzalloc_obj(), which explicitly zeroes out allocated memory, kmalloc_obj() returns raw heap memory that may contain sensitive data from previous allocations by other kernel processes or subsystems. This distinction is crucial because it determines whether uninitialized memory regions are exposed to external entities during subsequent operations.
The vulnerability manifests when the qla2x00_do_dport_diagnostics function executes a diagnostic request initiated by user space. The system allocates the necessary buffer using kmalloc_obj and proceeds to copy data from the kernel into this buffer via sg_copy_to_buffer for input processing, which only fills bytes corresponding to the user-provided payload length. Subsequently, when preparing the response, the code copies sizeof(*dd) bytes back to user space through sg_copy_from_buffer. However, while certain fields within the diagnostic structure are explicitly zeroed by qla26xx_dport_diagnostics, specifically the buf field, other critical components such as options and unused arrays remain uninitialized. Consequently, these residual memory regions containing arbitrary kernel heap contents are transmitted directly to the unprivileged user-space application making the request.
This behavior constitutes a classic information leak vulnerability where sensitive internal state of the operating system is exposed outside its intended boundary. The leaked data can include pointers, cryptographic keys, passwords, or other confidential information stored in previously used memory blocks on the kernel heap. Such exposure undermines the confidentiality guarantees provided by the OS and can facilitate further exploitation attempts, including address space layout randomization bypasses or logic flaws that rely on specific internal values being known to an attacker. The impact is particularly severe given that this functionality is accessible via standard device interfaces, potentially allowing local attackers with minimal privileges to extract valuable kernel memory contents across multiple invocations of the diagnostic interface.
From a classification perspective, this vulnerability aligns with CWE-200: Exposure of Sensitive Information to an Unauthorized Actor and falls under CWE-416: Use After Free if interpreted broadly in terms of accessing stale data, though more accurately it represents improper memory initialization leading to information disclosure. In the context of the MITRE ATT&CK framework for enterprise security, this technique corresponds to T1057: Process Discovery or more specifically T1083: File and Directory Discovery depending on how the leaked heap data is utilized by an attacker seeking reconnaissance within a compromised environment. It also relates to T1046: Network Service Scanning if used to fingerprint kernel versions based on memory layout patterns, although primarily it serves as direct information leakage via API calls.
To mitigate this vulnerability and prevent future occurrences of similar issues, the recommended remediation involves replacing kmalloc_obj with kzalloc_obj during buffer allocation for diagnostic responses. This change ensures that all allocated memory is zeroed before being populated or returned to user space, thereby eliminating any possibility of leaking residual kernel heap data. Additionally, developers should conduct thorough code reviews focusing on all paths where buffers are copied between kernel and user spaces to verify complete initialization of every field within the transferred structures. Implementing static analysis tools configured to detect uninitialized memory reads can help identify such oversights early in the development lifecycle. Furthermore, adopting stricter coding standards that mandate explicit zero-initialization for any buffer destined for external exposure would significantly reduce the attack surface associated with information disclosure vulnerabilities in kernel drivers.