{ "schemaVersion": 1, "attribution": [ { "source": "CISA Known Exploited Vulnerabilities", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog", "licence": "US government work" }, { "source": "GitHub Advisory Database", "url": "https://github.com/advisories", "licence": "CC BY 4.0" }, { "source": "Have I Been Pwned", "url": "https://haveibeenpwned.com/", "licence": "CC BY 4.0" }, { "source": "CVE Program (CVE records)", "url": "https://www.cve.org/Legal/TermsOfUse", "licence": "CVE Terms of Use", "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.", "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." }, { "source": "FIRST EPSS", "url": "https://www.first.org/epss/", "licence": "free to use; FIRST requests attribution" } ], "record": { "id": "CVE-2026-31588", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-31588", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-04-24T14:42:16.288Z", "updatedAt": "2026-10-19T18:55:59.596Z", "importedAt": "2026-10-24T01:58:02.025Z", "snapshot": { "id": "cve_2026-10-24_midnight_baseline", "at": "2026-10-24T00:00:00.000Z", "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z" }, "facts": { "title": "KVM: x86: Use scratch field in MMIO fragment to hold small write values", "summary": "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---", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "019d0bd32b9a4646ba35d904907452039e2db700" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "4569c66dd9e94a22cd0796b6514a8b25ffff16a1" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "52570e73d48f1c73836d37e594667117b4c2a5a8" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "dc6a6c3db3a4eca7e747cfc46e22c08d016c68f7" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "b5a02d37eb0739f462fa12df449ab9b3480c783b" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "22d2ff69d487a32a8b88f9c970120fc2daa08a77" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "2b83d91e9ae92fe1258d7040a32430bbb3bb7d6e" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "3a7b6d75c8f85b09dea893f64a85a356bcf6c3fe" }, { "version": "f78146b0f9230765c6315b2e14f56112513389ad", "status": "affected", "versionType": "git", "lessThan": "0b16e69d17d8c35c5c9d5918bf596c75a44655d3" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "3.5", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "3.5" }, { "version": "5.10.258", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.209", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.175", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.136", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.83", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.24", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "6.19.14", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.19.*" }, { "version": "7.0.1", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.0.*" }, { "version": "7.1", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }