{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-31588", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.120Z", "datePublished": "2026-04-24T14:42:16.288Z", "dateUpdated": "2026-04-24T14:42:16.288Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-04-24T14:42:16.288Z"}, "descriptions": [{"lang": "en", "value": "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": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/x86.c", "include/linux/kvm_host.h"], "versions": [{"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "b5a02d37eb0739f462fa12df449ab9b3480c783b", "status": "affected", "versionType": "git"}, {"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "22d2ff69d487a32a8b88f9c970120fc2daa08a77", "status": "affected", "versionType": "git"}, {"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "2b83d91e9ae92fe1258d7040a32430bbb3bb7d6e", "status": "affected", "versionType": "git"}, {"version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2", "lessThan": "3a7b6d75c8f85b09dea893f64a85a356bcf6c3fe", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["arch/x86/kvm/x86.c", "include/linux/kvm_host.h"], "versions": [{"version": "6.12.83", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.24", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.19.14", "lessThanOrEqual": "6.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0.1", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.12.83"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.18.24"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "6.19.14"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionEndExcluding": "7.0.1"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/b5a02d37eb0739f462fa12df449ab9b3480c783b"}, {"url": "https://git.kernel.org/stable/c/22d2ff69d487a32a8b88f9c970120fc2daa08a77"}, {"url": "https://git.kernel.org/stable/c/2b83d91e9ae92fe1258d7040a32430bbb3bb7d6e"}, {"url": "https://git.kernel.org/stable/c/3a7b6d75c8f85b09dea893f64a85a356bcf6c3fe"}], "title": "KVM: x86: Use scratch field in MMIO fragment to hold small write values", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "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---"}], "id": "CVE-2026-31588", "lastModified": "2026-04-24T17:51:40.810", "metrics": {}, "published": "2026-04-24T15:16:33.733", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/22d2ff69d487a32a8b88f9c970120fc2daa08a77"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/2b83d91e9ae92fe1258d7040a32430bbb3bb7d6e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/3a7b6d75c8f85b09dea893f64a85a356bcf6c3fe"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/b5a02d37eb0739f462fa12df449ab9b3480c783b"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Awaiting Analysis"}

{"bugzilla": {"description": "kernel: KVM: x86: Use scratch field in MMIO fragment to hold small write values", "id": "2461458", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2461458"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-825", "details": ["A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) component. This vulnerability, a use-after-free, occurs when KVM processes Memory-mapped I/O (MMIO) writes that span across different memory pages, and an internal temporary variable is used. A malicious guest operating system or a local user could exploit this by performing specific MMIO write operations, leading to KVM attempting to access memory that has already been released. This can result in memory corruption, which might allow for information disclosure or the execution of unauthorized code."], "name": "CVE-2026-31588", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2026-04-24T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31588\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31588\nhttps://lore.kernel.org/linux-cve-announce/2026042414-CVE-2026-31588-333a@gregkh/T"], "threat_severity": "Moderate"}

{}