CVE-2026-98814 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
nvme: fix command effects log lifetime for multipath heads
KASAN reported a use-after-free when an I/O passthrough command was sent through a multipath namespace head after the controller path that first created the head had been removed:
BUG: KASAN: slab-use-after-free in nvme_command_effects+0x192/0x200 [nvme_core]
Read of size 4 at addr ffff888141b14400 by task nvme/19811 nvme_command_effects+0x192/0x200 [nvme_core]
nvme_cmd_allowed+0x7e/0x1b0 [nvme_core]
nvme_user_cmd.constprop.0+0x1b5/0x450 [nvme_core]
nvme_ns_head_chr_ioctl+0xf4/0x2a0 [nvme_core]
Move the log cache to the subsystem, with one entry per command set. Both controllers and namespace heads hold subsystem references, keeping their log pointers valid until subsystem release.
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Analysis
by VulDB Data Team • 10/19/2026
The Linux kernel's NVMe driver contained a critical use-after-free vulnerability within the handling of multipath namespaces, specifically affecting the retrieval of command effects logs. This flaw was identified through Kernel Address Sanitizer (KASAN) reports indicating an invalid memory read operation in the nvme_command_effects function. The root cause lies in the lifecycle management of log caches associated with NVMe namespace heads. When a user-space application issues an I/O passthrough command via an ioctl interface, the kernel attempts to access specific controller or namespace data structures to validate and process that command. In multipath configurations, multiple paths can lead to the same logical namespace head. The vulnerability manifested when a path was removed from the system while another active path still held a reference to the shared namespace head structure. Because the log cache pointers were tied too closely to the specific controller instance rather than persisting at a higher abstraction level, removing one controller could inadvertently free memory that other paths or subsequent operations on the same namespace head still attempted to access.
This technical flaw represents a classic use-after-free condition where memory is deallocated while it is still in active use by another part of the system. From an architectural perspective, the issue stems from insufficient reference counting and lifetime management for subsystem-level resources within the NVMe core module. The original implementation allowed log pointers to become dangling if their associated controller was detached, even though the namespace head itself remained valid due to other active paths. This discrepancy between object lifetimes created a race condition window where concurrent access could trigger kernel crashes or potentially allow an attacker with local user privileges to exploit the invalid memory access for arbitrary code execution or denial of service against the host system.
The operational impact of this vulnerability is significant, particularly in enterprise environments utilizing NVMe over Fabrics or complex multipath storage setups. An unprivileged local user who can interact with NVMe devices through standard character device interfaces could trigger the faulty path by sending specific passthrough commands after a controller removal event. This would result in kernel panics due to the KASAN-detected slab-use-after-free error, leading to system instability and service interruption. Furthermore, depending on the memory layout at the time of exploitation, such use-after-free bugs can sometimes be leveraged for privilege escalation or information disclosure, although the primary immediate risk is availability through denial of service conditions caused by kernel oopses.
To mitigate this vulnerability, the Linux kernel maintainers implemented a structural change to move the command effects log cache from being tied to individual controllers or namespace heads to the subsystem level. By maintaining one entry per command set at the subsystem layer and ensuring that both controllers and namespace heads hold references to these subsystem resources, the fix guarantees that log pointers remain valid for as long as any component using them is active. This approach aligns with proper resource management practices where shared data structures are protected by reference counting mechanisms that prevent premature deallocation. Administrators should ensure their systems are updated with kernel versions containing this patch to close the security gap and maintain stability in multipath NVMe configurations.
From a classification standpoint, this vulnerability maps directly to CWE-416: Use After Free, which describes situations where pointers are used after they have been freed, leading to undefined behavior. In terms of attack vectors, it relates to ATT&CK technique T1059: Command and Scripting Interpreter if an attacker leverages the ioctl interface for malicious command execution, although the primary exploitation path here is through local privilege escalation or denial of service via kernel memory corruption. The fix emphasizes the importance of aligning object lifecycles with their actual usage patterns in complex driver architectures to prevent dangling pointer scenarios that compromise system integrity and security.