Linux Kernel up to 7.2.7/7.3-rc3 sched_ext kernel/sched/ext/ext.c scx_root_enable_workfn priv use after free

Summaryinfo

A vulnerability described as very critical has been identified in Linux Kernel up to 7.2.7/7.3-rc3. Affected by this issue is the function scx_root_enable_workfn of the file kernel/sched/ext/ext.c of the component sched_ext. Executing a manipulation of the argument priv can lead to use after free. This vulnerability appears as CVE-2026-98219. The attack requires local access. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.7/7.3-rc3. This vulnerability affects the function scx_root_enable_workfn of the file kernel/sched/ext/ext.c of the component sched_ext. The manipulation of the argument priv with an unknown input leads to a use after free vulnerability. The CWE definition for the vulnerability is CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Close the pre-enable ops error claim window scx_alloc_and_add_sched() publishes ops->priv before scx_root_enable_workfn() switches the state to SCX_ENABLING. An error claimed via scx_bpf_error_bstr() from an associated BPF program in that window is consumed by scx_disable_workfn(), which takes the pre-enable shortcut in scx_root_disable(). The shortcut returns without any teardown and restores SCX_DISABLED with an unconditional scx_set_enable_state() xchg racing the enable workfn's own transition. The enable then completes with the claim consumed: the scheduler stays up but can never be disabled again, and bpf_scx_unreg() frees it while still in use, resulting in a use-after-free. Both WARN_ON_ONCE()s fire back to back: WARNING: kernel/sched/ext/ext.c:7522 at scx_root_enable_workfn+0xeec/0x1be0, CPU#3: scx_enable_help/276 WARNING: kernel/sched/ext/ext.c:6398 at scx_root_disable+0xb50/0xdb8, CPU#0: sched_ext_helpe/664 scx_root_enable_workfn() switches to SCX_ENABLING before the scheduler allocation, so ops->priv is never visible while SCX_DISABLED. The allocation failure path restores SCX_DISABLED.

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-98219 since 09/25/2026. The exploitation appears to be easy. Local access is required to approach this attack. Additional levels of successful authentication are necessary for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 10/06/2026).

Upgrading to version 7.2.8 or 7.3-rc4 eliminates this vulnerability. Applying the patch 959c66dc4a915be306c35691095c787c61dc7df9/c7a1c6e8004ab12a9c9bfdcb603f60f9bf4a3cee is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.3-rc1
• 7.3-rc2
• 7.3-rc3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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