EUVD-2026-67558
GHSA-r646-7cf5-pgjc
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
AC:H over NVD's AC:L because triggering the vulnerability requires RISC-V hardware with a non-standard DRAM base alignment, a hardware-specific precondition absent from most deployments.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
riscv/mm: use physical alignment for vmemmap_start_pfn
RISC-V computes vmemmap_start_pfn by rounding phys_ram_base down to VMEMMAP_ADDR_ALIGN. That alignment must therefore be expressed in the physical-address domain.
Commit 476849b0fba4 ("riscv/mm: align vmemmap to maximal folio size") attempted to account for the maximal folio alignment by feeding MAX_FOLIO_VMEMMAP_ALIGN directly into VMEMMAP_ADDR_ALIGN. However, MAX_FOLIO_VMEMMAP_ALIGN is measured in bytes of struct page storage, whereas VMEMMAP_ADDR_ALIGN is used to align a physical address.
The mask-based compound_info encoding requires pfn_to_page(0) to be naturally aligned to MAX_FOLIO_VMEMMAP_ALIGN. Commit 9f94db4c7eaa ("mm/sparse: check memmap alignment for compound_info_has_mask()") added a check for that requirement and exposed the unit mismatch on systems such as QEMU virt, where the DRAM base is not aligned to MAX_FOLIO_NR_PAGES * PAGE_SIZE.
Here is the log: [ 0.000000][ C0] ------------[ cut here ]------------ [ 0.000000][ C0] WARNING: mm/sparse.c:365 at sparse_init+0x58a/0x6fe, CPU#0: swapper/0 [ 0.000000][ C0] Modules linked in: [ 0.000000][ C0] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 7.2.0-rc3-g1d8304bdd65f #2 PREEMPT [ 0.000000][ C0] Hardware name: riscv-virtio,qemu (DT) [ 0.000000][ C0] epc : sparse_init+0x58a/0x6fe [ 0.000000][ C0] ra : sparse_init+0x58a/0x6fe [ 0.000000][ C0] epc : ffffffff86851c88 ra : ffffffff86851c88 sp : ffffffff88807a30 [ 0.000000][ C0] gp : ffffffff8a3bf240 tp : ffffffff88842080 t0 : ff600000ffab6000 [ 0.000000][ C0] t1 : 000000017fab6000 t2 : 65203a6573726363 s0 : ffffffff88807bc0 [ 0.000000][ C0] s1 : 000000000e000000 a0 : 0000000000000007 a1 : 0000000000000000 [ 0.000000][ C0] a2 : 0000000000000002 a3 : ffffffff86851c88 a4 : 0000000000000000 [ 0.000000][ C0] a5 : ffffffff88843080 a6 : 0000000000000003 a7 : 0000000000000000 [ 0.000000][ C0] s2 : ff60000000000000 s3 : 0040000000000000 s4 : 0004000000000000 [ 0.000000][ C0] s5 : ffffffff8a4d92e0 s6 : ff600000ffab55e0 s7 : ffffffff88384d00 [ 0.000000][ C0] s8 : 0000000000000003 s9 : ffffffff88384cc1 s10: ffffffff88384cc0 [ 0.000000][ C0] s11: ffffffff8a4daae0 t3 : ffffffff915e8b20 t4 : ffffffff915e8b20 [ 0.000000][ C0] t5 : ffffffff915e8b20 t6 : ffffffff915e8bc8 ssp : 0000000000000000 [ 0.000000][ C0] status: 0000000200000100 badaddr: ffffffff86851c88 cause: 0000000000000003 [ 0.000000][ C0] [<ffffffff86851c88>] sparse_init+0x58a/0x6fe [ 0.000000][ C0] [<ffffffff8683d396>] mm_core_init_early+0x116/0x1e30 [ 0.000000][ C0] [<ffffffff86801edc>] start_kernel+0xd2/0x848
Convert MAX_FOLIO_VMEMMAP_ALIGN to the equivalent physical alignment before using it in VMEMMAP_ADDR_ALIGN. This keeps the existing round_down() logic while making the resulting vmemmap base satisfy the mask-alignment requirement.
AnalysisAI
Incorrect unit conversion in the RISC-V memory management subsystem causes vmemmap_start_pfn to be computed with a physically misaligned base, violating the mask-alignment requirement for compound_info encoding in the sparse memory model. Linux kernel versions incorporating commit 476849b0fba4 on RISC-V hardware where DRAM base is not aligned to MAX_FOLIO_NR_PAGES × PAGE_SIZE are affected - a condition confirmed on QEMU virt machines and potentially other RISC-V platforms. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three concurrent conditions: (1) a RISC-V architecture Linux system - x86, ARM, and other architectures are entirely unaffected; (2) a kernel version that includes commit 476849b0fba4 but not the subsequent stable fix commits (i.e., Linux 7.1 or 7.2-rc builds prior to the fix); and (3) a physical or emulated DRAM base that is not aligned to MAX_FOLIO_NR_PAGES × PAGE_SIZE - confirmed on QEMU virt machines and potentially other RISC-V platforms with non-standard memory placement. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD-assigned CVSS 7.8 (AV:L/AC:L/PR:L) implies a straightforward local exploitation path to full system compromise, but several signals temper that reading. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to Linux kernel 7.2 or Linux 7.1.8, which incorporate the corrected unit conversion for MAX_FOLIO_VMEMMAP_ALIGN before it is applied in VMEMMAP_ADDR_ALIGN. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Inventory Linux systems running RISC-V architecture and identify kernel versions incorporating commit 476849b0fba4, prioritizing production systems. …
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