CVE-2026-31777

Vulnerability

Overview

CVE-2026-31777 is a medium-severity vulnerability in the Linux kernel's ALSA ctxfi sound driver. The driver's daio_device_index() function can return an error value under certain conditions, but the calling code did not validate the return value before using it as an index. This missing error check means that an invalid index could be used in subsequent operations, potentially leading to out-of-bounds access or other undefined behavior [1][2].

Exploitation

Prerequisites and Attack Surface

To exploit this vulnerability, an attacker would need local access to the system and the ability to interact with the ALSA subsystem, for example by sending crafted audio control commands. No special privileges beyond normal user access to sound devices are required. The attack surface is limited to systems using the ctxfi driver, which is typically found in hardware with Creative Sound Blaster X-Fi or similar audio chipsets.

Impact

If triggered, the bug could cause the kernel to access memory outside of allocated arrays, leading to a classic out-of-bounds read or write. This could result in a denial of service (system crash or hang) or, in more severe scenarios, information disclosure or privilege escalation. The CVSS v3 base score of 5.5 reflects a medium severity, indicating a notable but not critical risk.

Mitigation

The fix has been applied in the Linux kernel stable tree via commits [1] and [2]. Users should update their kernel to a version that includes these patches. No workaround is available other than applying the kernel update. The vulnerability is not known to be exploited in the wild as of the publication date.