CVE-2026-68153 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
libceph: remove debugfs files before client teardown
ceph_destroy_client() tears down the monitor client before removing the per-client debugfs files. A concurrent read of the monmap debugfs file can enter monmap_show() after ceph_monc_stop() has freed monc->monmap, triggering a use-after-free.
Remove the debugfs files before stopping the OSD and monitor clients. debugfs_remove() drains active handlers and prevents new accesses, so the debugfs callbacks can no longer race the rest of client teardown.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability in question affects the linux kernel's ceph storage client implementation where a use-after-free condition can occur during client teardown operations. This issue specifically impacts the libceph subsystem which handles communication with ceph monitoring services. The flaw arises from an improper sequence of operations within the ceph_destroy_client() function that manages the cleanup process for ceph clients.
The technical root cause involves the timing relationship between removing debugfs files and stopping client components. During normal operation, the ceph client maintains debugfs entries for monitoring purposes including monmap debugfs files that expose monitor map information. When ceph_destroy_client() executes, it first tears down the monitor client by calling ceph_monc_stop() which frees the monc->monmap structure containing monitor mapping data. However, this cleanup sequence occurs before the debugfs files are removed from the filesystem.
This ordering issue creates a race condition where concurrent processes attempting to read the monmap debugfs file can trigger monmap_show() function execution after the memory pointed to by monc->monmap has already been freed. The use-after-free vulnerability occurs because the debugfs callback handler attempts to access memory that has been deallocated, potentially leading to system instability or security implications.
The operational impact of this vulnerability extends beyond simple system crashes as it represents a classic memory safety issue that could be exploited by malicious actors. The race condition allows for potential information disclosure through memory corruption or privilege escalation opportunities depending on the execution context. This type of vulnerability aligns with common weakness enumerations such as CWE-416 which addresses use-after-free conditions and CWE-362 which covers race conditions in concurrent systems.
The mitigation strategy implemented addresses this flaw by changing the teardown sequence within ceph_destroy_client() to remove debugfs files before stopping the monitor and OSD clients. This approach leverages the debugfs_remove() function which provides proper synchronization by draining active handlers and preventing new accesses to the removed entries. The solution ensures that all debugfs callbacks are properly terminated and cannot access freed memory structures during the subsequent client teardown operations.
This fix aligns with established security practices for managing cleanup sequences in kernel modules, particularly when dealing with concurrent access patterns and shared memory resources. The approach follows defensive programming principles by ensuring proper resource ordering and preventing race conditions between component teardown phases. The solution demonstrates a robust understanding of kernel memory management and concurrent access control mechanisms that are fundamental to maintaining system integrity in enterprise storage environments.
The vulnerability highlights the importance of careful resource management in kernel subsystems where multiple components must coordinate their cleanup operations. It underscores how seemingly simple ordering issues can create complex security implications in distributed storage systems that handle sensitive data across networked environments. This type of flaw is particularly concerning in production systems where storage reliability and data integrity are paramount considerations for enterprise deployments.
The resolution methodology reflects industry best practices for kernel security hardening, specifically addressing the ATT&CK technique T1068 which involves exploit for privilege escalation through improper resource handling. By ensuring proper cleanup sequencing before memory deallocation, the fix prevents potential exploitation pathways that could leverage the use-after-free condition for system compromise. This approach demonstrates comprehensive understanding of both the specific vulnerability and broader security implications within kernel subsystems that interface with critical enterprise storage infrastructures.