CVE-2023-54153: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54153 is a memory leak (kmemleak) vulnerability in the Linux kernel's ext4 filesystem driver. When ext4_mark_recovery_complete() returns an error during a failed mount operation, the error handling path fails to turn off previously enabled disk quotas, resulting in unreferenced kernel memory objects. The vulnerability affects the Linux kernel and was publicly disclosed on December 24, 2025. It carries a CVSS v3.1 base score of 5.5 (Medium), exploitable locally by a low-privileged user with no user interaction required (Red Hat Advisory, Red Hat Bugzilla).

The root cause is improper resource cleanup (CWE-401: Missing Release of Memory after Effective Lifetime) in the ext4 filesystem's mount failure path. Specifically, when ext4_mark_recovery_complete() returns an error inside __ext4_fill_super(), the code path does not invoke ext4_quota_off_umount() to release quota structures that were allocated during ext4_enable_quotas(). This leaves kernel memory objects — allocated via kmalloc_trace within v2_read_file_info and dquot_load_quota_sb — unreferenced and unfreed. The fix introduces a failed_mount10 label in the error handling path that explicitly calls ext4_quota_off_umount() to properly release the enabled quotas (Red Hat Bugzilla).

Successful triggering of this vulnerability results in a kernel memory leak, degrading system availability over time as unreferenced memory objects accumulate without being freed. There is no confidentiality or integrity impact — the vulnerability is limited to availability (kernel memory exhaustion). In practice, repeated triggering could contribute to system instability or denial of service on affected Linux systems running ext4 filesystems with quota support enabled (Red Hat Advisory, Red Hat Bugzilla).

The fix has been merged into the Linux kernel stable tree via multiple commits (e.g., 77c3ca1108eb, c327b83c59ee, d13f99632748, deef86fa3005), introducing a failed_mount10 error label that calls ext4_quota_off_umount() on mount failure. Users should update to a patched kernel version that includes these fixes. Red Hat has tracked this issue with low priority/severity; users of Red Hat-based distributions should monitor for updated kernel packages. As a workaround, avoiding the use of ext4 quota features on systems where untrusted filesystem images may be mounted can reduce exposure (Red Hat Bugzilla, Red Hat Advisory).