EUVD-2026-64418
GHSA-39hf-rf3c-rjqv
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Race condition timing requirement elevates AC to H; PR:L reflects required low-privilege local access; high C/I/A retained given kernel use-after-free impact potential.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
sched_ext: Skip sub-disable teardown for never-linked sub-schedulers
A sub-scheduler enable can fail before scx_link_sched() links the sched into the hierarchy, e.g. when the parent is already being disabled, and cleanup still runs the full scx_sub_disable().
That is racy against root disable: drain_descendants() is the only ordering between a sub's disable-time task walk and root disable's all-task teardown, and an unlinked sub is invisible to it. Root's teardown can thus run between the never-linked sub's drain and its walk, exiting every task to no scheduler.
The walk then trips the membership WARN and re-homes the exited tasks onto the dying hierarchy, a use-after-free.
Skip the cgroup ownership reset and the task walk if @sch was never linked, indicated by the empty ->sibling as unlinking only happens later in the same function. The membership WARN remains valid: a linked sub is always waited on by an ancestor's drain.
AnalysisAI
Use-after-free in the Linux kernel's sched_ext (extensible BPF scheduler) subsystem allows a local low-privileged attacker to corrupt kernel memory, potentially achieving full confidentiality, integrity, and availability compromise of the affected system. The race condition arises when a sub-scheduler enable fails before being linked into the scheduler hierarchy, yet the full teardown path still executes concurrently against root scheduler disable, causing tasks to be re-homed onto an already-freed scheduler hierarchy. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local system access with low-privilege credentials (PR:L per vendor CVSS vector). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor CVSS score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) accurately reflects the local-only attack vector and high impact triad, but the AC:L rating is optimistic: exploiting the race window between scx_sub_disable() and root disable's drain_descendants() requires precise timing, making practical exploitation substantially harder than a straightforward low-complexity bug. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | The primary remediation is to upgrade to a patched kernel version: Linux 7.1.9 (stable) or Linux 7.2 (next stable), both of which include the fix per EUVD data. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, consult vendor security advisory to identify affected Linux kernel versions and audit infrastructure to inventory vulnerable systems, prioritizing by business criticality and scope of local user access. …
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