CVE-2025-22090 is a vulnerability identified in the Linux kernel's memory management subsystem, specifically related to the handling of the Page Attribute Table (PAT) flags during the fork() system call on x86 architectures. The issue arises in the function copy_page_range(), which is responsible for duplicating the virtual memory areas (VMAs) and page tables when a process forks. When the helper function track_pfn_copy() fails during this process, the destination VMA is added to the maple tree without proper reservation or copying of page tables. Subsequently, during cleanup after the fork failure, untrack_pfn() attempts to access PAT information from page tables that were never copied, leading to a failure. The root cause is improper management of the VM_PAT flag: it is set prematurely before successful reservation and copying, and simply clearing this flag upon failure does not correctly undo reservations, potentially leaving inconsistent state. The fix involves setting the VM_PAT flag only after a successful reservation and ensuring that any partial reservations are properly undone if copying fails. This prevents untrack_pfn() from accessing invalid PAT data and avoids kernel crashes or undefined behavior. The vulnerability can be triggered reliably, as demonstrated by a provided reproducer, and manifests as kernel warnings or panics related to get_pat_info() and untrack_pfn() calls. Although this flaw does not appear to have been exploited in the wild yet, it poses a risk of local denial of service or kernel instability due to improper memory management during process creation.

For European organizations relying on Linux-based systems, especially servers and infrastructure running x86 architectures, this vulnerability could lead to system instability or crashes during process creation via fork(), which is a fundamental operation for many applications and services. This can result in denial of service conditions affecting critical services, including web servers, databases, and containerized environments. Since the flaw occurs at the kernel level, it could potentially disrupt multi-tenant environments or cloud services that depend on Linux virtualization and container technologies. Although exploitation requires local code execution (e.g., ability to invoke fork() with specific memory conditions), attackers who gain limited access could leverage this bug to cause kernel panics, leading to service outages. This is particularly impactful for industries with high availability requirements such as finance, healthcare, and telecommunications. Additionally, kernel instability might open avenues for privilege escalation or further exploitation if combined with other vulnerabilities, increasing the threat surface. The absence of known exploits in the wild reduces immediate risk but does not eliminate the need for prompt remediation.

European organizations should prioritize updating Linux kernels to versions where this vulnerability is patched. Since the issue is deep in the kernel memory management code, applying official Linux kernel updates from trusted distributors is the most effective mitigation. For environments where immediate patching is challenging, organizations should restrict untrusted local code execution and limit user privileges to reduce the risk of triggering the flaw. Monitoring kernel logs for warnings related to get_pat_info() or untrack_pfn() can help detect attempts to exploit or accidental triggers of the bug. In containerized or virtualized environments, isolating workloads and enforcing strict resource and process creation limits can reduce exposure. Additionally, organizations should review their incident response plans to quickly address potential denial of service incidents stemming from kernel crashes. Engaging with Linux distribution vendors for timely patches and testing updates in staging environments before production deployment is recommended to ensure stability and security.