CVE-2022-48935 is a use-after-free (UAF) vulnerability identified in the Linux kernel's netfilter subsystem, specifically within the nf_tables flowtable hooks management. The vulnerability arises due to improper unregistration of flowtable hooks upon network namespace (netns) exit. The kernel fails to unregister these hooks before releasing them via nf_tables_flowtable_destroy(), leading to a situation where the hook core attempts to access freed memory, resulting in a use-after-free condition. This flaw is evidenced by kernel address sanitizer (KASAN) reports indicating reads from freed memory addresses during the execution of nf_hook_entries_grow(). The vulnerability is rooted in the lifecycle management of flowtable hooks: __nft_release_hook() calls nft_unregister_flowtable_net_hooks() to unregister hooks, but the subsequent cleanup and freeing of flowtable entries (both software and hardware) occur after a Read-Copy-Update (RCU) grace period. If the hooks are not properly unregistered before this cleanup, the kernel may access invalid memory, causing instability or potential exploitation. Exploiting this vulnerability could allow an attacker with the ability to manipulate netfilter flowtables—likely requiring local privileges or specific network namespace configurations—to trigger kernel memory corruption. This could lead to denial of service (kernel panic) or potentially privilege escalation if exploited in conjunction with other vulnerabilities. The affected versions correspond to specific Linux kernel commits identified by their hashes, indicating this is a recent and targeted fix. No known exploits are currently reported in the wild, and no CVSS score has been assigned yet. The vulnerability affects Linux kernels utilizing the nf_tables framework for packet filtering and flow offloading, which is widely used in modern Linux distributions for firewalling and network traffic control.

For European organizations, the impact of CVE-2022-48935 can be significant, particularly for those relying on Linux-based infrastructure for critical network functions such as firewalls, routers, and virtualized network environments. The vulnerability could lead to kernel crashes causing denial of service, disrupting business operations, especially in sectors like finance, telecommunications, and critical infrastructure where uptime and network security are paramount. Additionally, if combined with other vulnerabilities, it could facilitate privilege escalation attacks, potentially allowing attackers to gain unauthorized control over affected systems. This risk is heightened in multi-tenant environments such as cloud service providers and data centers prevalent in Europe, where network namespaces and containerization are extensively used. The lack of known exploits reduces immediate risk, but the complexity and critical nature of the kernel component involved necessitate prompt attention to prevent future exploitation. Furthermore, regulatory frameworks like GDPR impose strict requirements on data protection and system integrity, so any compromise or downtime could have legal and financial repercussions for European entities.

To mitigate CVE-2022-48935, European organizations should: 1) Apply the latest Linux kernel patches that address this vulnerability as soon as they become available from their distribution vendors. Given the kernel commit hashes provided, tracking vendor advisories for updated kernel packages is critical. 2) Implement strict access controls to limit who can manipulate netfilter configurations and network namespaces, reducing the attack surface. 3) Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) in testing environments to detect similar memory corruption issues proactively. 4) Monitor kernel logs and system behavior for signs of instability or crashes related to netfilter operations, enabling early detection of exploitation attempts. 5) In containerized or virtualized environments, isolate network namespaces carefully and restrict capabilities that allow modification of flowtables. 6) Maintain an up-to-date inventory of Linux kernel versions in use across the organization to prioritize patching efforts. 7) Collaborate with Linux distribution vendors and security communities to stay informed about emerging exploits or additional mitigations related to this vulnerability.