CVE-2024-42094

Vulnerability

CVE-2024-42094 is a security issue in the Linux kernel's net/iucv subsystem, specifically related to the use of CPU mask variables. Prior to the fix, the code allocated a cpumask_t variable directly on the stack. When the kernel is compiled with CONFIG_CPUMASK_OFFSTACK=y, such stack allocation is discouraged because it can lead to a stack overflow [1].

Exploitation

This vulnerability is local in nature and does not require special privileges to trigger. An attacker with local access could potentially exploit the stack overflow by inducing conditions that cause the kernel to use a large CPU mask, overflowing the stack. The attack surface is the Linux kernel's IUCV (Inter-User Communication Vehicle) networking code, which is primarily used on IBM mainframes (S/390) [2].

Impact

A successful exploitation could lead to a denial of service (system crash) or potentially allow an attacker to escalate privileges if the overflow corrupts critical kernel data. The CVSS v3 base score of 7.1 (High) reflects the significant impact given the relatively low attack complexity [1].

Mitigation

The fix was introduced in the Linux kernel via commit be4e1304419c [4]. Using *cpumask_var API functions ensures that the CPU mask is dynamically allocated when CONFIG_CPUMASK_OFFSTACK is enabled, avoiding stack overflows. Users should update to a kernel version containing this patch or apply the relevant backport to affected systems [2].