CVE-2023-54320: 
Linux Kernel vulnerability analysis and mitigation

CVE-2023-54320 is a memory leak vulnerability in the Linux kernel's AMD Power Management Controller (PMC) driver, specifically in the amd_pmc_stb_debugfs_open_v2() function. When amd_pmc_send_cmd() fails during STB (Smart Trace Buffer) debug mechanism operations, the allocated buffer buf is not properly released, resulting in a memory leak. The vulnerability was published on December 30, 2025, and affects Linux kernel versions prior to the fixes introduced in 6.3.4 and 6.4. The CVSS base score is not formally assigned (estimated Medium severity by Feedly) (Feedly, EUVD).

The root cause is a missing memory deallocation on an error path in the amd_pmc_stb_debugfs_open_v2() function within the Linux kernel's platform/x86/amd/pmc driver (CWE-401: Missing Release of Memory after Effective Lifetime). When the function is invoked with the STB debug mechanism enabled and amd_pmc_send_cmd() returns a failure, the previously allocated buf pointer is not freed before the function returns, causing a kernel memory leak. Exploitation requires local access to a system with an AMD PMC and the STB debugfs interface enabled. Fixes were committed to the stable kernel tree at commits d804adef7b23b22bb82e1b3dd113e9073cea9bc1 and f6e7ac4c35a28aef0be93b32c533ae678ad0b9e7 (Feedly, EUVD).

The vulnerability causes a kernel memory leak on AMD systems with the PMC STB debug interface enabled. Repeated triggering of the error path can gradually exhaust kernel memory, potentially degrading system stability or availability. There is no evidence of confidentiality or integrity impact, and the vulnerability does not enable privilege escalation or remote code execution.

Apply the upstream Linux kernel patches that fix the memory leak: commit d804adef7b23b22bb82e1b3dd113e9073cea9bc1 (stable) and f6e7ac4c35a28aef0be93b32c533ae678ad0b9e7 (stable), included in kernel versions 6.3.4 and 6.4 respectively. Linux distribution maintainers (e.g., Red Hat) have also tracked this issue for backporting. As a workaround, disabling the AMD PMC STB debugfs interface (if not required) reduces exposure. Users should update to a patched kernel version as the primary remediation (EUVD, Feedly).