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CVE-2025-39881 is a use-after-free vulnerability in the Linux kernel's kernfs polling path for cgroup Pressure Stall Information (PSI) monitoring. Disabling pressure monitoring releases PSI triggers through cgroup_file_release() and frees the open file's private context through kernfs_drain_open_files(), while epoll can retain a reference to the file. Re-enabling monitoring permits subsequent polling through kernfs_fop_poll(), cgroup_file_poll(), cgroup_pressure_poll(), and psi_trigger_poll() to access the freed context. A KASAN diagnostic identified an eight-byte read from freed memory in psi_trigger_poll(). The vulnerability can cause kernel denial of service and potentially privilege escalation, depending on exploitability in the affected kernel build and configuration.
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A Linux kernel use-after-free vulnerability occurs when cgroup pressure monitoring is disabled and re-enabled while epoll continues monitoring an open pressure file. Released PSI trigger data can subsequently be accessed during polling. The reference assigns a CVSS v3 score of 7.8, with local access, low privileges, and high confidentiality, integrity, and availability impact. The fix prevents operations on released open files by using kernfs_get_active_of() to acquire active references.
A Linux kernel use-after-free vulnerability in kernfs polling during PSI monitoring. Disabling cgroup pressure monitoring releases file-private data while epoll retains a reference; re-enabling monitoring can cause polling to access the freed data. The reported CVSS v3 base score is 7.8, indicating local exploitation requiring low privileges and potentially high confidentiality, integrity, and availability impacts. The fix prevents further operations on released open files by introducing kernfs_get_active_of().
A local use-after-free vulnerability in the Linux kernel's kernfs polling and Pressure Stall Information monitoring. Disabling cgroup.pressure releases monitoring data while epoll retains a file reference; re-enabling monitoring can cause polling to access freed memory. The fix prevents operations on released open files by using kernfs_get_active_of(). The advisory assigns a CVSS v3 base score of 7.8 and recommends updating Echo linux packages to version 6.1.153-1 or later.
A high-severity local Linux kernel use-after-free flaw in kernfs/PSI pressure-monitoring polling. A race between releasing a cgroup pressure-monitoring file and epoll polling can access freed open-file state. The fix introduces active references for kernfs open files via kernfs_get_active_of().
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