CVE-2024-46852 is a vulnerability identified in the Linux kernel's dma-buf subsystem, specifically within the CMA (Contiguous Memory Allocator) heap fault handler. The issue arises from an off-by-one error in the boundary check when handling page faults beyond the end of a dma-buf buffer. Prior to the introduction of the VM_DONTEXPAND flag in commit 1c1914d6e8c6, it was possible to create a memory mapping larger than the actual buffer size using the mremap system call, effectively bypassing the overflow checks in dma_buf_mmap_internal. When a page fault occurs beyond the buffer boundary, the CMA heap fault handler attempts to validate the fault offset against the buffer size but incorrectly calculates the boundary by one page. This off-by-one error can lead to reading beyond the allocated pages array and inserting an arbitrary page into the mapping. Such behavior could potentially allow an attacker with local access to manipulate memory mappings, leading to unauthorized memory access or corruption. The vulnerability affects multiple versions of the Linux kernel identified by the commit hash a5d2d29e24be8967ef78a1b1fb2292413e3b3df9. Although no known exploits are currently reported in the wild, the flaw represents a subtle memory management bug that could be leveraged in privilege escalation or information disclosure attacks if combined with other vulnerabilities or misconfigurations. The fix involves correcting the boundary check to prevent reading off the end of the pages array, thereby eliminating the possibility of inserting arbitrary pages into the mapping and ensuring proper enforcement of buffer size limits during memory remapping and fault handling.

For European organizations, this vulnerability poses a risk primarily to systems running affected Linux kernel versions, which are widely deployed across enterprise servers, cloud infrastructure, and embedded devices. Exploitation could allow local attackers or malicious processes to gain unauthorized access to memory regions, potentially leading to privilege escalation or data leakage. This is particularly concerning for critical infrastructure, financial institutions, and government agencies that rely heavily on Linux-based systems for secure operations. The ability to bypass memory boundary checks undermines kernel memory protection mechanisms, increasing the attack surface for advanced persistent threats (APTs) and insider threats. Although remote exploitation is unlikely without prior access, the vulnerability could be chained with other exploits to compromise system integrity and confidentiality. Given the prevalence of Linux in European data centers and cloud environments, unpatched systems could face increased risk of targeted attacks aiming to disrupt services or exfiltrate sensitive data. The absence of known exploits in the wild currently reduces immediate threat levels but does not eliminate the potential for future weaponization by threat actors.

European organizations should prioritize updating their Linux kernels to versions that include the patch fixing CVE-2024-46852. Since the vulnerability involves low-level kernel memory management, applying vendor-provided security updates or recompiling kernels with the fix is essential. System administrators should audit their environments to identify systems running affected kernel versions, especially those exposed to untrusted users or running multi-tenant workloads. Employing strict access controls and minimizing local user privileges can reduce the risk of exploitation. Additionally, organizations should monitor kernel logs and system behavior for unusual memory mapping activities that could indicate attempts to exploit this flaw. For environments where immediate patching is not feasible, deploying kernel hardening techniques such as SELinux or AppArmor policies to restrict memory operations may provide temporary mitigation. Finally, maintaining robust endpoint detection and response (EDR) capabilities can help detect suspicious local activity indicative of exploitation attempts.