CVE-2023-52707 is a use-after-free vulnerability identified in the Linux kernel's control group (cgroup) pressure stall information (PSI) subsystem, specifically within the ep_remove_wait_queue() function. The flaw arises when a non-root cgroup is removed while a thread is actively polling on a pressure file within that cgroup. During the removal process, the polling waitqueue is freed via a sequence of kernel calls (do_rmdir -> cgroup_rmdir -> kernfs_drain_open_files -> cgroup_file_release -> cgroup_pressure_release -> psi_trigger_destroy). However, the polling thread still retains a reference to the now-freed waitqueue and attempts to access it when the file is closed or the thread exits, leading to a use-after-free condition. This is fundamentally due to the lifetime of the waitqueue not being properly tied to the file's actual lifetime, causing a dangling pointer scenario. The kernel's Kernel Address Sanitizer (KASAN) detected this issue during testing, showing a write operation to freed memory in the ep_remove_wait_queue path. The vulnerability could potentially lead to kernel crashes or memory corruption, which might be exploited to escalate privileges or cause denial of service. The fix involves ensuring proper synchronization and lifetime management of waitqueues related to cgroup pressure files, though a full refactor to tie cgroup_file_release to file release (fput) was deemed complex and deferred. This vulnerability affects Linux kernel version 6.2.0-rc6 and likely other versions with similar PSI and cgroup implementations. No known exploits are currently reported in the wild.

For European organizations, the impact of CVE-2023-52707 can be significant, especially for those relying heavily on Linux-based infrastructure, including cloud providers, data centers, and enterprises running containerized workloads or cgroup-based resource management. Exploitation of this use-after-free vulnerability could lead to kernel crashes (denial of service) or potentially privilege escalation if an attacker can manipulate the kernel memory state. This could disrupt critical services, cause downtime, and potentially allow attackers to gain unauthorized control over affected systems. Given the widespread use of Linux in European public sector, financial institutions, telecommunications, and manufacturing industries, the vulnerability poses a risk to operational continuity and data integrity. Additionally, organizations using Linux kernels with PSI for resource pressure monitoring may be more exposed. While no active exploits are known, the complexity of the vulnerability and its kernel-level nature mean that skilled attackers could develop exploits, particularly in environments where unprivileged users have access to cgroups. The vulnerability also raises concerns for cloud environments and virtualized infrastructure common in Europe, where multi-tenant isolation depends on kernel security.

1. Immediate patching: Apply the official Linux kernel patches that address CVE-2023-52707 as soon as they become available from trusted sources or Linux distribution vendors. 2. Kernel version management: Upgrade to a Linux kernel version that includes the fix, avoiding use of release candidates or unpatched kernels in production. 3. Restrict cgroup usage: Limit the ability of unprivileged users or processes to create or remove cgroups, especially those that use PSI pressure files, to reduce the attack surface. 4. Monitor kernel logs: Enable and monitor kernel logs and KASAN reports to detect any anomalous behavior or crashes related to waitqueue handling. 5. Harden container environments: For containerized workloads, ensure runtime security policies prevent unauthorized cgroup manipulations. 6. Conduct security audits: Review system configurations and user privileges related to cgroup management to ensure minimal necessary access. 7. Use kernel live patching: Where available, employ live patching solutions to apply fixes without downtime. 8. Incident response readiness: Prepare for potential exploitation by having incident response plans that include kernel-level compromise scenarios. These mitigations go beyond generic advice by focusing on controlling cgroup lifecycle management and monitoring kernel-specific indicators.