PoC Exploit Released for Use-After-Free Vulnerability in Linux Kernel’s POSIX CPU Timers Implementation

Cybersecurity Update: Linux Kernel Vulnerability CVE-2025-38352

A proof-of-concept (PoC) exploit has been released for CVE-2025-38352 , a race condition vulnerability affecting the Linux kernel's POSIX CPU timer implementation.

The flaw allows attackers to initiate use-after-free conditions in kernel memory, potentially leading to privilege escalation and system compromise. CVE-2025-38352 occurs in the handle_posix_cpu_timers() function, which processes timer signals during CPU scheduler ticks. The vulnerability exploits a timing window between the collection and processing of firing timers, enabling an attacker to free timer structures while they are still accessed.

Field Value

CVE ID CVE-2025-38352

Vulnerability Type Race condition use-after-free in Linux kernel POSIX CPU timers

Affected Component handle_posix_cpu_timers() in the Linux kernel POSIX CPU timers implementation

Affected Versions Linux LTS 6.12.33 (and related vulnerable builds, especially 32-bit Android kernels)

Impact Potential local privilege escalation via kernel memory corruption

The vulnerability affects systems with CONFIG_POSIX_CPU_TIMERS_TASK_WORK disabled, making it particularly relevant to 32-bit Android devices. Exploitation requires a zombie process state and precise timing coordination to trigger the race condition.

The PoC, published on GitHub, illustrates how an attacker can:

Create a POSIX CPU timer that fires after a specific CPU time interval. Force a thread into a zombie state during critical kernel operations. Reap the zombie task while timer processing is underway. Delete the timer through the timer_delete() syscall, causing premature memory deallocation. Trigger a use-after-free when the kernel continues accessing the freed timer.

Exploitation results in KASAN memory sanitizer warnings indicating UAF write operations in the posix_timer_queue_signal() function. On non-KASAN systems, kernel warnings appear in the send_sigqueue() function.

Kernel patches have been released through the Linux kernel's stable branches. Users should update to patched kernel versions immediately to prevent exploitation. The fix eliminates the race window by preventing zombie processes from executing timer handling code.

System administrators are advised to prioritize patching, especially for Android devices and embedded Linux systems using vulnerable kernel versions. The availability of the public PoC accelerates the risk timeline for unpatched systems.

Based on reporting by Cyber Security News.