The ALSA dummy sequencer port incorrectly copied a smaller legacy event structure for an UMP event and then read a larger UMP packet from the same stack buffer. This caused the process to read past the end of the temporary stack object, exposing kernel stack contents and potentially leading to a crash. The flaw is a classic buffer overread weakness that could be leveraged by an attacker to obtain sensitive data or to destabilize the system.

All Linux kernels that contain the ALSA sequencer module without the commit that implements the fix are affected. The patch is referenced via several kernel commit IDs and is intended to ensure the correct union storage is used. Users running any kernel version prior to the inclusion of those commits are susceptible.

The vulnerability is local to the ALSA subsystem; an attacker who can send crafted UMP events to the dummy client could trigger the overread. EPSS and KEV scores are not provided. No CVSS score is included in the data. The attack does not require network access, so the risk depends on the ability of local users or processes to interact with ALSA. If exploited, it could allow data leakage or a denial of service by crashing a user or service that engages with ALSA.