Linux Kernel up to 7.2.12 sched_ext scx_bypass release of resource

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 7.2.12. Affected is the function scx_bypass of the component sched_ext. This manipulation causes release of resource. This vulnerability is registered as CVE-2026-99104. Remote exploitation of the attack is possible. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 7.2.12 and classified as critical. Affected by this vulnerability is the function scx_bypass of the component sched_ext. The manipulation with an unknown input leads to a release of resource vulnerability. The CWE definition for the vulnerability is CWE-772. The product does not release a resource after its effective lifetime has ended, i.e., after the resource is no longer needed. As an impact it is known to affect availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: sched_ext: Fix the bypass dispatch claim for schedulers bypassed by an ancestor scx_bypass() claims bypass dispatch when the scheduler's depth goes from zero to one and releases it when the depth returns to zero, but propagates only the depth to the descendants, not the claim. A descendant that starts bypassing with its ancestor never claims, and one whose own bypass ends under the ancestor's keeps its claim, as its depth does not return to zero. A sub-scheduler enable whose bypass ends under a PM suspend thus leaks its claim: the parent keeps hosting bypass dispatch and the sub-scheduler's next bypass trips the WARN_ON_ONCE() on the claim. A sub-scheduler disable that starts under a PM suspend has no claim, so once the resume lifts the root's bypass its tasks sit on the parent's bypass DSQs with nobody consuming them. Claim for every descendant whose depth goes from zero to one in the propagation and release every scheduler in the subtree whose depth returned to zero once the tasks have moved out of the bypass DSQs. A parent that is bypassing itself when a descendant claims consumes only its own bypass DSQs, empty until it leaves bypass and becomes the host.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-99104 since 09/25/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/28/2026). The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 7.2.13 eliminates this vulnerability. Applying the patch f0f18075e45d47bef7ff2eb9512ee4f0c7e5f9c7/5bdeca322a6f8d10acaf67cccab1f69747ee7be3 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
• 7.2.8
• 7.2.9
• 7.2.10
• 7.2.11
• 7.2.12

License

• open-source

Website

• Vendor: https://www.kernel.org/

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