CVE-2024-56772 is a high-severity use-after-free (UAF) vulnerability in the Linux kernel's KUnit testing framework, specifically within the string-stream handling code. The flaw occurs in the kunit_init_suite() function during the initialization of test suites. When the function kunit_debugfs_create_suite() calls alloc_string_stream() inside a loop iterating over test cases, a failure in allocation leads to an error path that frees the previously assigned suite->log stream memory but does not reset the pointer to NULL. Subsequently, string_stream_clear() is called on this dangling pointer, causing a use-after-free condition. This results in a kernel memory access violation, leading to kernel panics and potential system crashes. The vulnerability is identified by the kernel panic logs showing an invalid memory access at a virtual address outside the user and kernel address ranges, indicating corruption of kernel memory. The issue affects specific Linux kernel versions identified by commit hashes and was fixed by ensuring the stream pointer is set to NULL after freeing, preventing the UAF. The vulnerability has a CVSS v3.1 score of 7.8, reflecting high impact on confidentiality, integrity, and availability, with low attack complexity but requiring local privileges and no user interaction. Exploitation could allow an attacker with limited privileges to cause denial of service via kernel panic or potentially escalate privileges by exploiting kernel memory corruption. No known exploits are currently reported in the wild. The vulnerability is classified under CWE-416 (Use After Free).

For European organizations, this vulnerability poses a significant risk primarily to systems running vulnerable Linux kernel versions that include the affected KUnit testing framework code. Since the flaw can cause kernel panics and system crashes, it can lead to denial of service conditions on critical infrastructure, servers, and embedded devices running Linux. In environments where Linux is used extensively, such as cloud providers, data centers, telecommunications, and industrial control systems, this could disrupt operations and availability. Moreover, the potential for privilege escalation through kernel memory corruption could allow attackers to gain unauthorized root access, threatening confidentiality and integrity of sensitive data. Given the widespread use of Linux in European government agencies, enterprises, and critical infrastructure, the impact could be substantial if exploited. However, exploitation requires local privileges, limiting remote attack vectors but increasing risk from insider threats or compromised accounts. The absence of known exploits in the wild reduces immediate risk but emphasizes the need for proactive patching to prevent future attacks.

European organizations should promptly identify and update all Linux systems running affected kernel versions to the latest patched releases where the UAF bug in kunit_init_suite() is fixed. Since the vulnerability requires local privileges, organizations should enforce strict access controls and limit user permissions to reduce the attack surface. Employ kernel hardening techniques such as Kernel Address Space Layout Randomization (KASLR), Kernel Page Table Isolation (KPTI), and use of security modules like SELinux or AppArmor to mitigate exploitation impact. Regularly audit and monitor kernel logs for unusual crashes or panics that could indicate exploitation attempts. For environments using automated testing frameworks or continuous integration pipelines that utilize KUnit, ensure these components are updated and isolated from production systems. Additionally, implement robust endpoint detection and response (EDR) solutions capable of detecting anomalous kernel-level activities. Finally, maintain an inventory of Linux kernel versions deployed across the organization to facilitate rapid vulnerability management and patch deployment.