CVE-2025-39994
HighCVSS 7.3Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
In the xc5000 tuner driver in the Linux kernel, a use-after-free vulnerability exists in xc5000_release(). Using cancel_delayed_work() does not guarantee that the delayed work item timer_sleep has finished, leading to a race condition where memory is freed while the work item still runs.
Risk Assessment
An attacker can exploit this race to gain unauthorized access to kernel memory, potentially leading to privilege escalation or system crash.
Recommendation
Apply the patch that replaces cancel_delayed_work() with cancel_delayed_work_sync() to safely cancel the work item before freeing memory.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: media: tuner: xc5000: Fix use-after-free in xc5000_release The original code uses cancel_delayed_work() in xc5000_release(), which does not guarantee that the delayed work item timer_sleep has fully completed if it was already running. This leads to use-after-free scenarios where xc5000_release() may free the xc5000_priv while timer_sleep is still active and attempts to dereference the xc5000_priv. A typical race condition is illustrated below: CPU 0 (release thread) | CPU 1 (delayed work callback) xc5000_release() | xc5000_do_timer_sleep() cancel_delayed_work() | hybrid_tuner_release_state(priv) | kfree(priv) | | priv = container_of() // UAF Replace cancel_delayed_work() with cancel_delayed_work_sync() to ensure that the timer_sleep is properly canceled before the xc5000_priv memory is deallocated. A deadlock concern was considered: xc5000_release() is called in a process context and is not holding any locks that the timer_sleep work item might also need. Therefore, the use of the _sync() variant is safe here. This bug was initially identified through static analysis. [hverkuil: fix typo in Subject: tunner -> tuner]