Linux Kernel up to 7.0.11 KVM access_zcr_el2 information disclosure

Summaryinfo

A vulnerability has been found in Linux Kernel up to 7.0.11 and classified as problematic. This affects the function access_zcr_el2 of the component KVM. Performing a manipulation results in information disclosure. This vulnerability is identified as CVE-2026-63941. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.0.11. It has been classified as problematic. This affects the function access_zcr_el2 of the component KVM. The manipulation with an unknown input leads to a information disclosure vulnerability. CWE is classifying the issue as CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. This is going to have an impact on confidentiality. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor ZCR_EL2 can be updated by a VHE guest hypervisor either using ZCR_EL2 (which traps) or ZCR_EL1 (which does not trap). KVM handles both in different way: - on ZCR_EL2 trap, ZCR_EL2.LEN is immediately capped at the VM's own VL limit. This has the potential to break existing SW that relies on the full LEN field to be stateful. - on ZCR_EL1 access, we do absolutely nothing. On restoring the SVE context for an L2 guest, we directly restore the guest hypervisor's view of ZCR_EL2 into the physical ZCR_EL2. If the guest's view of the register was updated using the ZCR_EL2 accessor, the value has already been sanitised (with the caveat mentioned above). But if the guest used ZCR_EL1, the raw value is written into the HW, and the L2 guest can now access VLs that it shouldn't. Fix all the above by moving the VL capping to the restore points, ensuring that: - the HW is always programmed with a capped value, irrespective of the accessor being used, - the ZCR_EL2.LEN field is always completely stateful, irrespective of the accessor being used. Additionally, move ZCR_EL2 to be a sanitised register, ensuring that only the LEN field is actually stateful. This requires some creative construction of the RES0 mask, as the sysreg generation script does not yet generate RAZ/WI fields. [maz: rewrote commit message, tidy up access_zcr_el2()]

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2026-63941 since 07/19/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. The exploitation needs additional levels of successful authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 07/19/2026). MITRE ATT&CK project uses the attack technique T1592 for this issue.

Upgrading to version 7.0.12 eliminates this vulnerability.

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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
• 7.0.10
• 7.0.11

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

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