CVE-2026-90325
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel, blk-cgroup's blkcg_activate_policy() can race with concurrent blkcg deletion when switching IO schedulers, leading to a use-after-free in rcu_accelerate_cbs. The issue occurs when a blkg is being destroyed while blkcg_activate_policy() tries to get a reference to it.
Risk Assessment
May lead to use-after-free in the kernel, potentially enabling privilege escalation or system hang.
Recommendation
Update the Linux kernel to a version containing the fix that checks hlist_unhashed(&blkg->blkcg_node) before getting a reference to the blkg.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: skip dying blkg in blkcg_activate_policy() When switching IO schedulers on a block device, blkcg_activate_policy() can race with concurrent blkcg deletion, leading to a use-after-free in rcu_accelerate_cbs. T1: T2: blkg_destroy kill(&blkg->refcnt) // blkg->refcnt=1->0 blkg_release // call_rcu(__blkg_release) ... blkg_free_workfn ->pd_free_fn(pd) elv_iosched_store elevator_switch ... iterate blkg list blkg_get(blkg) // blkg->refcnt=0->1 list_del_init(&blkg->q_node) blkg_put(pinned_blkg) // blkg->refcnt=1->0 blkg_release // call_rcu again rcu_accelerate_cbs // uaf Fix this by checking hlist_unhashed(&blkg->blkcg_node) before getting a reference to the blkg. This is the same check used in blkg_destroy() to detect if a blkg has already been destroyed. If the blkg is already unhashed, skip processing it since it's being destroyed.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

