# CVE-2026-31600: arm64: mm: Handle invalid large leaf mappings correctly CVE-2026-31600 is fixed in 19 products on 1 platform, first by ALAS2023-2026-1693, released May 8, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-31600 - Priority: High - CVSS: 7.5 (Moderate) - EPSS: 0.0029 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Apr 24, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-31600 ## Description In the Linux kernel, the following vulnerability has been resolved: arm64: mm: Handle invalid large leaf mappings correctly It has been possible for a long time to mark ptes in the linear map as invalid. This is done for secretmem, kfence, realm dma memory un/share, and others, by simply clearing the PTE_VALID bit. But until commit a166563e7ec37 ("arm64: mm: support large block mapping when rodata=full") large leaf mappings were never made invalid in this way. It turns out various parts of the code base are not equipped to handle invalid large leaf mappings (in the way they are currently encoded) and I've observed a kernel panic while booting a realm guest on a BBML2_NOABORT system as a result: [ 15.432706] software IO TLB: Memory encryption is active and system is using DMA bounce buffers [ 15.476896] Unable to handle kernel paging request at virtual address ffff000019600000 [ 15.513762] Mem abort info: [ 15.527245] ESR = 0x0000000096000046 [ 15.548553] EC = 0x25: DABT (current EL), IL = 32 bits [ 15.572146] SET = 0, FnV = 0 [ 15.592141] EA = 0, S1PTW = 0 [ 15.612694] FSC = 0x06: level 2 translation fault [ 15.640644] Data abort info: [ 15.661983] ISV = 0, ISS = 0x00000046, ISS2 = 0x00000000 [ 15.694875] CM = 0, WnR = 1, TnD = 0, TagAccess = 0 [ 15.723740] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 [ 15.755776] swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000081f3f000 [ 15.800410] [ffff000019600000] pgd=0000000000000000, p4d=180000009ffff403, pud=180000009fffe403, pmd=00e8000199600704 [ 15.855046] Internal error: Oops: 0000000096000046 [#1] SMP [ 15.886394] Modules linked in: [ 15.900029] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc4-dirty #4 PREEMPT [ 15.935258] Hardware name: linux,dummy-virt (DT) [ 15.955612] pstate: 21400005 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) [ 15.986009] pc : __pi_memcpy_generic+0x128/0x22c [ 16.006163] lr : swiotlb_bounce+0xf4/0x158 [ 16.024145] sp : ffff80008000b8f0 [ 16.038896] x29: ffff80008000b8f0 x28: 0000000000000000 x27: 0000000000000000 [ 16.069953] x26: ffffb3976d261ba8 x25: 0000000000000000 x24: ffff000019600000 [ 16.100876] x23: 0000000000000001 x22: ffff0000043430d0 x21: 0000000000007ff0 [ 16.131946] x20: 0000000084570010 x19: 0000000000000000 x18: ffff00001ffe3fcc [ 16.163073] x17: 0000000000000000 x16: 00000000003fffff x15: 646e612065766974 [ 16.194131] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 [ 16.225059] x11: 0000000000000000 x10: 0000000000000010 x9 : 0000000000000018 [ 16.256113] x8 : 0000000000000018 x7 : 0000000000000000 x6 : 0000000000000000 [ 16.287203] x5 : ffff000019607ff0 x4 : ffff000004578000 x3 : ffff000019600000 [ 16.318145] x2 : 0000000000007ff0 x1 : ffff000004570010 x0 : ffff000019600000 [ 16.349071] Call trace: [ 16.360143] __pi_memcpy_generic+0x128/0x22c (P) [ 16.380310] swiotlb_tbl_map_single+0x154/0x2b4 [ 16.400282] swiotlb_map+0x5c/0x228 [ 16.415984] dma_map_phys+0x244/0x2b8 [ 16.432199] dma_map_page_attrs+0x44/0x58 [ 16.449782] virtqueue_map_page_attrs+0x38/0x44 [ 16.469596] virtqueue_map_single_attrs+0xc0/0x130 [ 16.490509] virtnet_rq_alloc.isra.0+0xa4/0x1fc [ 16.510355] try_fill_recv+0x2a4/0x584 [ 16.526989] virtnet_open+0xd4/0x238 [ 16.542775] __dev_open+0x110/0x24c [ 16.558280] __dev_change_flags+0x194/0x20c [ 16.576879] netif_change_flags+0x24/0x6c [ 16.594489] dev_change_flags+0x48/0x7c [ 16.611462] ip_auto_config+0x258/0x1114 [ 16.628727] do_one_initcall+0x80/0x1c8 [ 16.645590] kernel_init_freeable+0x208/0x2f0 [ 16.664917] kernel_init+0x24/0x1e0 [ 16.680295] ret_from_fork+0x10/0x20 [ 16.696369] Code: 927cec03 cb0e0021 8b0e0042 a9411c26 (a900340c) [ 16.723106] ---[ end trace 0000000000000000 ]--- [ 16.752866] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b [ 16.792556] Kernel Offset: 0x3396ea200000 from 0xffff8000800000 ---truncated--- ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.18 amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel-livepatch-6.18.25-55.108 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | linux Debian 14 | 6.19.14-1 | [DEBIAN-CVE-2026-31600](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31600.md) | May 15, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.25-55.108.amzn2023 | [ALAS2023-2026-1693](https://patchblox.com/security/data/fix/linux/alas2023-2026-1693.md) | May 8, 2026 | --- Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.