CVE-2023-53173: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-53173 is a memory leak vulnerability in the Linux kernel's TTY subsystem, specifically in the pcn_uart driver's debugfs handling. When debugfs_lookup() is called, the returned dentry must have dput() called on it to release the reference; failure to do so causes memory to leak over time. The vulnerability affects Linux kernel versions before 5.15.100, 5.16 through 6.1.17, and 6.2 through 6.2.4. It was disclosed on September 15, 2025, and carries a CVSS v3.1 base score of 5.5 (Medium) (Red Hat Advisory, Red Hat Bugzilla).

The root cause is classified as CWE-401 (Missing Release of Memory after Effective Lifetime). In the pcn_uart driver, a call to debugfs_lookup() returns a dentry object whose reference count is incremented, but the code never calls dput() to decrement it, resulting in a kernel memory leak that accumulates over time. The fix replaces debugfs_lookup() with debugfs_lookup_and_remove(), which internally handles both the lookup and the proper reference release in a single atomic operation. Exploitation requires local, low-privileged access to the system (Red Hat Advisory, Red Hat Bugzilla).

Successful exploitation causes gradual kernel memory exhaustion, which can degrade system performance, increase resource consumption, and potentially lead to system instability or a denial-of-service condition. There is no impact on confidentiality or data integrity; the sole impact is on availability. The vulnerability is limited in scope to the local system and does not facilitate lateral movement or data exfiltration (Red Hat Advisory).

Update the Linux kernel to a patched version: 5.15.100 or later (for the 5.15.x stable branch), 6.1.18 or later (for the 6.1.x stable branch), or 6.2.5 or later (for the 6.2.x branch). The fix is also included in kernel 6.3 and all subsequent releases. As a compensating control, restrict local system access to minimize the attack surface, and monitor system memory usage for unusual consumption patterns. Upstream patches are available via the stable kernel tree (Red Hat Bugzilla, Kernel Patch 5.15.x, Kernel Patch 6.1.x).