CVE-2023-53729

Root

Cause

The vulnerability resides in the Qualcomm MSM (QMI) encode/decode helper (qmi_encdec) within the Linux kernel's soc subsystem. The QMI TLV (Type-Length-Value) elements define string fields with a maximum length, and many element info structures account for the null terminator by using a buffer of MAX_LEN + 1. However, the decode logic does not verify that the incoming string length is strictly less than MAX_LEN + 1 before appending a null character. If a string is exactly MAX_LEN + 1 bytes long, the null terminator write will access one byte beyond the allocated buffer, triggering an out-of-bounds write [1][2][3].

Exploitation & Attack Surface

No special privileges are required to trigger this bug locally; it can be reached through any code path that decodes a QMI message containing a string field of maximum length. An attacker with the ability to send crafted QMI messages—for example, through a netlink socket or a Qualcomm IPC channel—can deliberately set a string field to its maximum permitted length to provoke the out-of-bounds condition. No authentication is needed if the interface is accessible from userspace, making this a local privilege escalation vector [1][2][3].

Impact

Successful exploitation leads to a kernel-stack buffer overflow, which can corrupt adjacent stack data. An attacker may leverage this to overwrite a return address or other critical kernel structures, ultimately achieving arbitrary code execution in the kernel context. This can result in a full system compromise, including privilege escalation and denial of service (system crash) [1][2][3].

Mitigation & Status

The fix has been applied in upstream Linux kernel releases following the identification of the bug. Stable kernel updates contain the patch that adds a proper length check before appending the null terminator. System administrators should apply the latest stable kernel updates from their distribution. No workaround is available short of updating the kernel [1][2][3].