Linux Kernel up to 7.2.8/7.3-rc4 KVM _gaccess_shadow_fault unusual condition

Summaryinfo

A vulnerability identified as very critical has been detected in Linux Kernel up to 7.2.8/7.3-rc4. Affected is the function _gaccess_shadow_fault of the component KVM. This manipulation causes unusual condition. The identification of this vulnerability is CVE-2026-98653. The attack can only be executed locally. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.8/7.3-rc4. It has been declared as very critical. Affected by this vulnerability is the function _gaccess_shadow_fault of the component KVM. The manipulation with an unknown input leads to a unusual condition vulnerability. The CWE definition for the vulnerability is CWE-754. The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: KVM: s390: Fix _gaccess_shadow_fault() In some circumstances, it is possible that the page of nested guest memory that is being shadowed is not present at all in the parent guest gmap. dat_entry_walk() will not find any leaf entry and return with -ENOENT, which will erroneously be propagated all the way to userspace. Fix by manually calling gmap_link() on the memory of the nested guest that is being shadowed if the mapping was not already present.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-98653 since 09/25/2026. The exploitation appears to be easy. Attacking locally is a requirement. Additional levels of successful authentication are needed for exploitation. 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 10/18/2026).

Upgrading to version 7.2.9 or 7.3-rc5 eliminates this vulnerability. Applying the patch 94c43c7df46433ed4d1e18f13770b019ba977bd8/faff4c8ff3dbec6d71b89dd281a0d17c4478fa44 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
• 7.3-rc1
• 7.3-rc2
• 7.3-rc3
• 7.3-rc4

License

• open-source

Website

• Vendor: https://www.kernel.org/

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