CVE-2024-44965 is a vulnerability identified in the Linux kernel affecting the x86 architecture, specifically related to the memory management subsystem. The issue arises in the function pti_clone_pgtable(), which is responsible for cloning page tables during process isolation with Page Table Isolation (PTI) enabled. The vulnerability stems from incorrect assumptions about memory alignment in the function's implementation. While the code assumes that the start address is aligned to a Page Middle Directory (PMD) boundary, this assumption holds true for x86_64 architectures but not for i386 (32-bit) architectures. This misalignment can cause the loop termination condition in pti_clone_pgtable() to malfunction, resulting in a 'short' clone of the page table entries. Consequently, the user-space memory mapping may contain incomplete or truncated entries, particularly affecting executable text segments. This can lead to system instability, manifested as endless traps, stack exhaustion, and eventual #DF (Double Fault) exceptions triggered by the stack guard. The root cause is the use of an incorrect increment form for the address pointer, which fails to account for the alignment differences on i386. The fix involves correcting the increment logic to avoid alignment assumptions, ensuring proper cloning of page tables on all affected architectures. This vulnerability was reported by Guenter and has been addressed in recent Linux kernel updates. There are no known exploits in the wild at the time of publication, and no CVSS score has been assigned yet.

For European organizations, the impact of CVE-2024-44965 could be significant, particularly for those relying on Linux systems running on 32-bit x86 architectures. Although many modern systems have transitioned to 64-bit, legacy systems and embedded devices may still operate on i386 kernels. The vulnerability can cause system crashes and instability, potentially leading to denial of service conditions. In environments where uptime and reliability are critical, such as financial institutions, healthcare providers, and industrial control systems, these crashes could disrupt operations and lead to data loss or service unavailability. Additionally, incomplete or corrupted user-space memory mappings could be exploited indirectly to escalate privileges or bypass security controls, although no such exploits are currently known. The lack of a known exploit reduces immediate risk, but the presence of a kernel-level bug affecting memory management warrants prompt attention. Organizations using custom or older Linux distributions should verify their kernel versions and apply patches to mitigate potential risks. The vulnerability also highlights the importance of maintaining updated toolchains and kernel builds, as the issue was triggered by GCC-11 compiled kernels on i386-nosmp configurations.

To mitigate CVE-2024-44965, European organizations should: 1) Identify and inventory all Linux systems running on 32-bit x86 architectures, including embedded and legacy devices. 2) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from trusted sources or distribution vendors. 3) Rebuild custom kernels using updated toolchains that incorporate the fix, ensuring that the pti_clone_pgtable() function no longer makes incorrect alignment assumptions. 4) Test patched kernels in staging environments to confirm stability and absence of regressions, especially for systems with PTI enabled. 5) Monitor system logs for unusual trap or fault patterns that could indicate exploitation attempts or instability related to this issue. 6) Where possible, consider migrating legacy 32-bit systems to supported 64-bit architectures to reduce exposure to this and similar vulnerabilities. 7) Implement robust backup and recovery procedures to minimize operational impact in case of crashes. 8) Engage with Linux distribution vendors and security communities to stay informed about updates and best practices related to this vulnerability.