Linux Kernel up to 7.2.3 sched_ext scx_dispatch_sched race condition

Summaryinfo

A vulnerability labeled as very critical has been found in Linux Kernel up to 7.2.3. Affected by this issue is the function scx_dispatch_sched of the component sched_ext. Executing a manipulation can lead to race condition. This vulnerability is tracked as CVE-2026-89519. The attack can be launched remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.3. This vulnerability affects the function scx_dispatch_sched of the component sched_ext. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. 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: Replace SCX_RQ_BAL_KEEP with a dispatch verdict return SCX_RQ_BAL_KEEP tells the pick to keep running the previous task, a leftover from when balancing and picking were separate operations. An rq-level flag only works while dispatches and picks pair up one to one, which core scheduling breaks: selections interleave through dispatch's lock drops and a pick can consume a stale flag, keeping a task that has since been dequeued. Fixing core scheduling support requires the decision to travel with the dispatch that made it. Make scx_dispatch_sched() and balance_one() return an explicit verdict instead and drop the flag's plumbing from the tools autogen enum headers. Also factor the pick-side invocation, its follow-up queueing and the post-dispatch checks out of do_pick_task_scx() into dispatch_pick(). No functional changes intended. v2: Drop the SCX_RQ_BAL_KEEP plumbing from the tools autogen enum headers as well (Andrea).

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-89519 since 09/11/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/12/2026).

Upgrading to version 7.2.4 or 7.3-rc1 eliminates this vulnerability. Applying the patch 6f1d3bfe54430f8d54e0530a27f2ecbf8466576e/ffaab58d217581cb75353168f8812a16e10463fc 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

License

• open-source

Website

• Vendor: https://www.kernel.org/

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