CVE-2026-63941

CVE CVE-2026-63941EUVD EUVD-2026-45714Published 2026-07-19T14:55:37.000ZLast changed 2026-08-05T12:37:28.000ZCVSS 8.8

What the advisory describes

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()]

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux b3d29a8230998b36afecf494b199211d26052785 <83726330748981372bde86ed5411d7b306612991; b3d29a8230998b36afecf494b199211d26052785 <742a9b5ccd8c46caf983ca90c94f855466968e34; patch: 7.1; 6.11; patch: 0; patch: 7.0.12

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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