CVE-2026-98593 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
s390/debug: Fix NULL pointer dereference in debug_info_copy()
When debug_register_static() fails, it clears areas, active_pages and active_entries but leaves the area bounds unchanged. Copying such an area, either by opening its view file or via debug_dump(), makes debug_info_copy() dereference the NULL pointers.
Skip the copy loop when the source has no areas.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel on s390 architecture contains a critical flaw within the debugging subsystem that results in a null pointer dereference, specifically located in the debug_info_copy function. This vulnerability arises from an inconsistent state management issue during the initialization and error handling phases of static debug registration. When the debug_register_static routine encounters a failure condition, it attempts to clean up by clearing specific data structures such as areas, active_pages, and active_entries. However, this cleanup process fails to reset or validate the area bounds that define the scope of these data structures. Consequently, the kernel retains metadata indicating that valid memory regions exist even though the underlying pointers have been nullified.
The operational impact manifests when a user space application attempts to interact with the debug interface through standard mechanisms such as opening its view file or invoking debug_dump operations. These actions trigger the execution of debug_info_copy, which iterates over the area bounds without verifying whether the corresponding pointer arrays are actually populated. Because the cleanup logic left the bounds intact while nullifying the pointers, the copy function proceeds to dereference memory addresses that point to NULL. This leads to a kernel panic or system crash, effectively causing a denial of service for the affected system. The vulnerability highlights a common class of errors where error paths do not fully synchronize state variables with resource allocations.
From a classification perspective, this issue aligns with CWE-476, which denotes a null pointer dereference. This type of flaw is particularly dangerous in kernel space because it can be triggered by local users who have access to the debug filesystem or related interfaces. The attack vector typically involves interacting with device files associated with the s390 debugging infrastructure. In terms of adversarial tactics, this vulnerability relates to techniques found in MITRE ATT&CK that involve exploiting software vulnerabilities for denial of service or potentially escalating privileges if an attacker can leverage a crash to trigger other kernel behaviors, although the primary impact here is system stability and availability.
Mitigation strategies primarily focus on applying vendor-provided patches that correct the state management logic within debug_register_static. The fix ensures that when registration fails, all associated bounds are also cleared or invalidated, preventing subsequent copy operations from accessing null pointers. Administrators should ensure their systems are updated with the latest kernel versions for s390 architectures to resolve this inconsistency. Additionally, implementing strict access controls on debugging interfaces can reduce the attack surface by limiting which users can trigger these code paths. Regular auditing of error handling routines in kernel modules is also recommended to prevent similar state desynchronization issues that lead to null pointer dereferences.