In the Linux kernel, the following vulnerability has been resolved:
x86/apic: Don't disable x2APIC if locked
The APIC supports two modes, legacy APIC (or xAPIC), and Extended APIC (or x2APIC). X2APIC mode is mostly compatible with legacy APIC, but it disables the memory-mapped APIC interface in favor of one that uses MSRs. The APIC mode is controlled by the EXT bit in the APIC MSR.
The MMIO/xAPIC interface has some problems, most notably the APIC LEAK [1]. This bug allows an attacker to use the APIC MMIO interface to extract data from the SGX enclave.
Introduce support for a new feature that will allow the BIOS to lock the APIC in x2APIC mode. If the APIC is locked in x2APIC mode and the kernel tries to disable the APIC or revert to legacy APIC mode a GP fault will occur.
Introduce support for a new MSR (IA32_XAPIC_DISABLE_STATUS) and handle the new locked mode when the LEGACY_XAPIC_DISABLED bit is set by preventing the kernel from trying to disable the x2APIC.
On platforms with the IA32_XAPIC_DISABLE_STATUS MSR, if SGX or TDX are enabled the LEGACY_XAPIC_DISABLED will be set by the BIOS. If legacy APIC is required, then it SGX and TDX need to be disabled in the BIOS.
[1]: https://aepicleak.com/aepicleak.pdf
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Debian | — | Upgrade linux | Dec 29, 2025 | Dec 29, 2025 |
| Huawei Euleros 2_0_sp12 | — | Upgrade bpftoolUpgrade python3-perfUpgrade kernelUpgrade kernel-tools-libsUpgrade kernel-abi-stablelistsUpgrade kernel-tools | Mar 17, 2026 | Mar 16, 2026 |
| Huawei Euleros 2_0_sp13 | — | Upgrade kernel-toolsUpgrade kernelUpgrade bpftoolUpgrade kernel-tools-libsUpgrade kernel-abi-stablelistsUpgrade python3-perf | Mar 10, 2026 | Mar 10, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Dec 24, 2025 |
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