CVE-2025-21842 is a vulnerability identified in the Linux kernel specifically related to the AMD Kernel Fusion Driver (amdkfd) component, which is part of the AMD GPU driver stack. The issue arises from improper handling of a pointer parameter in the function amdgpu_amdkfd_free_gtt_mem. This function is designed to free graphics translation table (GTT) memory objects and expects a double pointer (void**) as its second argument. However, due to the permissive nature of the C language and GCC compiler, a single pointer (void*) can be implicitly cast and passed to this function without compilation errors. At runtime, the function dereferences the pointer expecting a void**, but if a void* is passed instead, this leads to erroneous behavior. The vulnerability manifests when the gang_ctx_bo (a buffer object related to user queue initialization in amdkfd) fails to initialize properly and the cleanup routine attempts to free it using this flawed pointer handling. This can cause memory corruption, use-after-free, or invalid memory access, potentially leading to kernel crashes (denial of service) or exploitable conditions for privilege escalation or arbitrary code execution within the kernel context. The vulnerability was reserved in late December 2024 and published in early March 2025. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The affected versions are identified by a specific commit hash, indicating this is a recent and targeted fix in the Linux kernel source code.

For European organizations, the impact of CVE-2025-21842 depends largely on their use of Linux systems with AMD GPUs, particularly those leveraging the amdkfd driver for GPU compute tasks such as HPC, AI workloads, or graphics processing. Exploitation could lead to kernel crashes causing service outages or, in worst cases, privilege escalation allowing attackers to gain root-level access. This is particularly critical for data centers, cloud providers, and enterprises running Linux-based infrastructure with AMD hardware. Disruption or compromise of such systems could affect confidentiality, integrity, and availability of sensitive data and services. Given the kernel-level nature of the vulnerability, successful exploitation could undermine system security controls and facilitate lateral movement within networks. While no exploits are known yet, the vulnerability's presence in a core kernel component means that once weaponized, it could be leveraged in targeted attacks or automated exploit campaigns. European organizations in sectors such as finance, healthcare, government, and critical infrastructure that rely on Linux servers with AMD GPUs are at higher risk. The impact is also heightened by the difficulty of detecting exploitation at the kernel level and the potential for persistent compromise.

To mitigate CVE-2025-21842, European organizations should prioritize updating their Linux kernel to the latest patched versions that include the fix for this vulnerability. Since the issue is related to a specific commit, verifying kernel versions against the patch is essential. Organizations should audit their systems to identify Linux hosts running AMD GPUs with the amdkfd driver enabled, especially those used for compute or graphics workloads. Disabling or unloading the amdkfd module temporarily can reduce risk if patching is delayed, though this may impact GPU functionality. Implementing strict access controls and monitoring for unusual kernel crashes or system instability can help detect potential exploitation attempts. Employing kernel integrity monitoring tools and enabling security modules such as SELinux or AppArmor can provide additional defense layers. For environments using containerization or virtualization, ensuring hypervisor and container runtime security is also important to prevent escalation from compromised guests. Finally, organizations should maintain up-to-date incident response plans that include kernel-level compromise scenarios and conduct regular vulnerability scanning and penetration testing focused on kernel vulnerabilities.