Linux Kernel up to 7.0.9 s390 apmask_store use after free

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 7.0.9. Affected by this vulnerability is the function apmask_store of the component s390. Performing a manipulation results in use after free. This vulnerability is known as CVE-2026-53116. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 7.0.9. This affects the function apmask_store of the component s390. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: s390/ap: use generic driver_override infrastructure When the AP masks are updated via apmask_store() or aqmask_store(), ap_bus_revise_bindings() is called after ap_attr_mutex has been released. This calls __ap_revise_reserved(), which accesses the driver_override field without holding any lock, racing against a concurrent driver_override_store() that may free the old string, resulting in a potential UAF. Fix this by using the driver-core driver_override infrastructure, which protects all accesses with an internal spinlock. Note that unlike most other buses, the AP bus does not check driver_override in its match() callback; the override is checked in ap_device_probe() and __ap_revise_reserved() instead. Also note that we do not enable the driver_override feature of struct bus_type, as AP - in contrast to most other buses - passes "" to sysfs_emit() when the driver_override pointer is NULL. Thus, printing "\n" instead of "(null)\n". Additionally, AP has a custom counter that is modified in the corresponding custom driver_override_store().

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-53116 since 06/09/2026. The exploitability is told to be easy. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 06/24/2026).

Upgrading to version 7.0.10 eliminates this vulnerability. Applying the patch 8f2eca0570438b94602da1297353eb7b10dcb6cb/81d6f7c3a70b10ff757ee8b5f8114a190871cf1e is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. 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

• 7.0.0
• 7.0.1
• 7.0.2
• 7.0.3
• 7.0.4
• 7.0.5
• 7.0.6
• 7.0.7
• 7.0.8
• 7.0.9

License

• open-source

Website

• Vendor: https://www.kernel.org/

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