CVE-2018-7566 in Linux
Summary
by MITRE
The Linux kernel 4.15 has a Buffer Overflow via an SNDRV_SEQ_IOCTL_SET_CLIENT_POOL ioctl write operation to /dev/snd/seq by a local user.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2018-7566 represents a critical buffer overflow condition within the Linux kernel version 4.15 that specifically affects the sound subsystem. This issue manifests through the SNDRV_SEQ_IOCTL_SET_CLIENT_POOL ioctl operation which is designed to manage client memory pools in the sequencer subsystem. The vulnerability arises when a local user with access to /dev/snd/seq device can manipulate the ioctl parameters to exceed buffer boundaries during memory allocation operations. This particular flaw resides in the kernel's sound subsystem implementation where improper bounds checking occurs during client pool configuration operations, creating an exploitable condition that can be leveraged for privilege escalation or system compromise.
The technical root cause of this vulnerability aligns with CWE-121, which describes the condition where a buffer is not properly bounded, leading to potential memory corruption. The flaw exists in the kernel's sequencer device driver where the SNDRV_SEQ_IOCTL_SET_CLIENT_POOL ioctl handler does not adequately validate the size parameter provided by userspace. When a local attacker submits a crafted size value that exceeds the allocated buffer space, the kernel's memory management routines can be manipulated to overwrite adjacent memory regions. This buffer overflow condition specifically targets the client pool configuration mechanism that manages memory allocation for sequencer clients, allowing attackers to write beyond intended memory boundaries and potentially corrupt kernel data structures or execute arbitrary code with kernel privileges.
The operational impact of CVE-2018-7566 extends beyond simple privilege escalation as it represents a significant security weakness in the Linux kernel's sound subsystem that can be exploited by any local user with access to the audio device. The attack vector is particularly concerning because it requires minimal privileges and can be executed through standard device access mechanisms. An attacker with local access can leverage this vulnerability to gain kernel-level privileges, potentially leading to complete system compromise and persistent access. The vulnerability's exploitation can result in denial of service conditions, data corruption, or more severe consequences including privilege escalation to root access. This makes the vulnerability particularly dangerous in multi-user environments where local access might be available to untrusted users or where privilege separation is insufficient.
Mitigation strategies for this vulnerability should focus on immediate kernel updates to versions that contain the patched implementation of the sound subsystem. System administrators should prioritize applying the relevant security patches from their distribution vendors as these updates typically include proper bounds checking and buffer size validation for the ioctl operations. Additionally, implementing proper access controls and privilege separation can reduce the attack surface by limiting local user access to the audio device files. Network administrators should consider disabling unnecessary sound subsystem components when they are not required for system operations, and monitoring for unusual ioctl operations on the sound device can help detect potential exploitation attempts. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques where local users can leverage kernel vulnerabilities to gain elevated privileges, making it a significant concern for system security hardening and compliance requirements. Organizations should also consider implementing kernel lockdown features and ensuring proper system hardening practices to minimize the risk of exploitation.