{"id":"CVE-2026-31588","revision":null,"records":[{"revision":"9787fa7413834469bb710c979784fb81","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-31588","aliases":[],"title":"KVM: x86: Use scratch field in MMIO fragment to hold small write values","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: x86: Use scratch field in MMIO fragment to hold small write values\n\nWhen exiting to userspace to service an emulated MMIO write, copy the\nto-be-written value to a scratch field in the MMIO fragment if the size\nof the data payload is 8 bytes or less, i.e. can fit in a single chunk,\ninstead of pointing the fragment directly at the source value.\n\nThis fixes a class of use-after-free bugs that occur when the emulator\ninitiates a write using an on-stack, local variable as the source, the\nwrite splits a page boundary, *and* both pages are MMIO pages. Because\nKVM's ABI only allows for physically contiguous MMIO requests, accesses\nthat split MMIO pages are separated into two fragments, and are sent to\nuserspace one at a time. When KVM attempts to complete userspace MMIO in\nresponse to KVM_RUN after the first fragment, KVM will detect the second\nfragment and generate a second userspace exit, and reference the on-stack\nvariable.\n\nThe issue is most visible if the second KVM_RUN is performed by a separate\ntask, in which case the stack of the initiating task can show up as truly\nfreed data.\n\n ==================================================================\n BUG: KASAN: use-after-free in complete_emulated_mmio+0x305/0x420\n Read of size 1 at addr ffff888009c378d1 by task syz-executor417/984\n\n CPU: 1 PID: 984 Comm: syz-executor417 Not tainted 5.10.0-182.0.0.95.h2627.eulerosv2r13.x86_64 #3\n Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.15.0-0-g2dd4b9b3f840-prebuilt.qemu.org 04/01/2014 Call Trace:\n dump_stack+0xbe/0xfd\n print_address_description.constprop.0+0x19/0x170\n __kasan_report.cold+0x6c/0x84\n kasan_report+0x3a/0x50\n check_memory_region+0xfd/0x1f0\n memcpy+0x20/0x60\n complete_emulated_mmio+0x305/0x420\n kvm_arch_vcpu_ioctl_run+0x63f/0x6d0\n kvm_vcpu_ioctl+0x413/0xb20\n __se_sys_ioctl+0x111/0x160\n do_syscall_64+0x30/0x40\n entry_SYSCALL_64_after_hwframe+0x67/0xd1\n RIP: 0033:0x42477d\n Code: <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48\n RSP: 002b:00007faa8e6890e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010\n RAX: ffffffffffffffda RBX: 00000000004d7338 RCX: 000000000042477d\n RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005\n RBP: 00000000004d7330 R08: 00007fff28d546df R09: 0000000000000000\n R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004d733c\n R13: 0000000000000000 R14: 000000000040a200 R15: 00007fff28d54720\n\n The buggy address belongs to the page:\n page:0000000029f6a428 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x9c37\n flags: 0xfffffc0000000(node=0|zone=1|lastcpupid=0x1fffff)\n raw: 000fffffc0000000 0000000000000000 ffffea0000270dc8 0000000000000000\n raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected\n\n Memory state around the buggy address:\n ffff888009c37780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n ffff888009c37800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n >ffff888009c37880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n ^\n ffff888009c37900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n ffff888009c37980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff\n ==================================================================\n\nThe bug can also be reproduced with a targeted KVM-Unit-Test by hacking\nKVM to fill a large on-stack variable in complete_emulated_mmio(), i.e. by\noverwrite the data value with garbage.\n\nLimit the use of the scratch fields to 8-byte or smaller accesses, and to\njust writes, as larger accesses and reads are not affected thanks to\nimplementation details in the emulator, but add a sanity check to ensure\nthose details don't change in the future. Specifically, KVM never uses\non-stack variables for accesses larger that 8 bytes, e.g. uses an operand\nin the emulator context, and *al\n---truncated---","state":0,"publishedAt":"2026-04-24T14:42:16.288+00:00","modifiedAt":"2026-10-19T18:55:59.596+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"arch/x86/kvm/x86.c\",\n \"include/linux/kvm_host.h\"\n ],\n \"versions\": [\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"019d0bd32b9a4646ba35d904907452039e2db700\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"4569c66dd9e94a22cd0796b6514a8b25ffff16a1\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"52570e73d48f1c73836d37e594667117b4c2a5a8\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"dc6a6c3db3a4eca7e747cfc46e22c08d016c68f7\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"b5a02d37eb0739f462fa12df449ab9b3480c783b\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"22d2ff69d487a32a8b88f9c970120fc2daa08a77\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"2b83d91e9ae92fe1258d7040a32430bbb3bb7d6e\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"3a7b6d75c8f85b09dea893f64a85a356bcf6c3fe\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"f78146b0f9230765c6315b2e14f56112513389ad\",\n \"lessThan\": \"0b16e69d17d8c35c5c9d5918bf596c75a44655d3\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"arch/x86/kvm/x86.c\",\n \"include/linux/kvm_host.h\"\n ],\n \"versions\": [\n {\n \"version\": \"3.5\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"3.5\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.10.258\",\n \"lessThanOrEqual\": \"5.10.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"5.15.209\",\n \"lessThanOrEqual\": \"5.15.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.175\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.136\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.83\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.24\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.19.14\",\n \"lessThanOrEqual\": \"6.19.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.0.1\",\n \"lessThanOrEqual\": \"7.0.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.1\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","score":8.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/019d0bd32b9a4646ba35d904907452039e2db700","https://git.kernel.org/stable/c/4569c66dd9e94a22cd0796b6514a8b25ffff16a1","https://git.kernel.org/stable/c/52570e73d48f1c73836d37e594667117b4c2a5a8","https://git.kernel.org/stable/c/dc6a6c3db3a4eca7e747cfc46e22c08d016c68f7","https://git.kernel.org/stable/c/b5a02d37eb0739f462fa12df449ab9b3480c783b","https://git.kernel.org/stable/c/22d2ff69d487a32a8b88f9c970120fc2daa08a77","https://git.kernel.org/stable/c/2b83d91e9ae92fe1258d7040a32430bbb3bb7d6e","https://git.kernel.org/stable/c/3a7b6d75c8f85b09dea893f64a85a356bcf6c3fe","https://git.kernel.org/stable/c/0b16e69d17d8c35c5c9d5918bf596c75a44655d3"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31588","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-31588","identifiers":["CVE-2026-31588"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. Missing entries do not establish absence of exploitation.","generation":"2026-11-08T21:02:31.8931850+00:00","complete":true,"records":1769,"lastAttemptAt":"2026-11-08T21:02:31.893185+00:00","lastSuccessAt":"2026-11-08T21:02:32.2143877+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:32.2146388+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"cve-program","scope":"Official CVE Program baseline and cumulative hourly delta; all vendors, published and rejected records","generation":"cve-eaa64dac63caa79c8d4905619258c41c51b39e461b996124e1a21b5e85e7e738-ea572f75aa62c370f36c9951285f437791ed77e310a361fa98b48744b8a4f391","complete":true,"records":421267,"lastAttemptAt":"2026-11-08T21:02:31.4333443+00:00","lastSuccessAt":"2026-11-08T20:47:19.8933196+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:31.4333443+00:00","snapshotPublishedAt":"2026-11-08T20:26:57+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"euvd","scope":"Rolling EUVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-45d47722bca14f09ac26662adb699591","complete":true,"records":13654,"lastAttemptAt":"2026-11-08T21:02:36.7086981+00:00","lastSuccessAt":"2026-11-08T20:47:46.939+00:00","error":null,"lastVerifiedAt":"2026-11-08T20:47:46.939+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13706,"expectedIdentifiers":13706,"failedIdentifiers":0},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. Not a global EPSS backfill.","generation":"2026-11-08T21:02:31.8931850+00:00","complete":true,"records":1096,"lastAttemptAt":"2026-11-08T21:02:31.893185+00:00","lastSuccessAt":"2026-11-08T21:02:32.3894193+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:32.38942+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-ddc095a411c54633beb68aaff30b70cb","complete":true,"records":13666,"lastAttemptAt":"2026-11-08T21:02:34.4952279+00:00","lastSuccessAt":"2026-11-08T21:02:34.481+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:34.481+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13706,"expectedIdentifiers":13706,"failedIdentifiers":0},{"source":"osv:Go","scope":"Complete OSV Go ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"go-980593e6977a6d1b4fb1eed5a1ffe88a468736f89f0a06f710924ad59132c023","complete":true,"records":9914,"lastAttemptAt":"2026-11-08T21:02:31.7841816+00:00","lastSuccessAt":"2026-11-08T11:07:07.068788+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:31.7841816+00:00","snapshotPublishedAt":"2026-11-08T11:02:46+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:NuGet","scope":"Complete OSV NuGet ecosystem archive, including GitHub Advisory Database records; NuGet version matching only","generation":"nuget-fde804134ecdda0ddd5ff5c26ee1fff5a6fa659311f7ef2e51c6ad54964db0e2","complete":true,"records":1971,"lastAttemptAt":"2026-11-08T21:02:31.5325642+00:00","lastSuccessAt":"2026-11-06T19:03:17.0399903+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:31.5325642+00:00","snapshotPublishedAt":"2026-11-06T18:17:57+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:crates.io","scope":"Complete OSV crates.io ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"crates.io-964c14035e6f0f6478b2870fad6a7ef9f6045876d4a12af2c2e514521e54b6af","complete":true,"records":3055,"lastAttemptAt":"2026-11-08T21:02:31.8040207+00:00","lastSuccessAt":"2026-11-08T11:07:12.1927025+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:31.8040207+00:00","snapshotPublishedAt":"2026-11-08T11:02:46+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"osv:npm","scope":"Complete OSV npm ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"npm-f8647d7ba64b1ba0dfdc7130944766d5b36d5b77d18fff0c79e651a4cff3c2b9","complete":true,"records":231293,"lastAttemptAt":"2026-11-08T21:02:31.6506398+00:00","lastSuccessAt":"2026-11-08T11:06:56.2918717+00:00","error":null,"lastVerifiedAt":"2026-11-08T21:02:31.6506398+00:00","snapshotPublishedAt":"2026-11-08T11:02:50+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null}]}