{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-64456", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T15:36:31.789Z", "datePublished": "2026-07-25T08:51:24.659Z", "dateUpdated": "2026-08-17T04:56:00.610Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:56:00.610Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nhwrng: virtio: clamp device-reported used.len at copy_data()\n\nrandom_recv_done() stores the device-reported used.len directly into\nvi->data_avail. copy_data() then indexes vi->data[] using\nvi->data_idx (advanced by previous copy_data() calls) and issues a\nmemcpy() without re-validating either value against the posted\nbuffer size sizeof(vi->data) (SMP_CACHE_BYTES bytes, typically 32\nor 64).\n\nA malicious or buggy virtio-rng backend can set used.len beyond\nsizeof(vi->data), steering the memcpy() past the end of the inline\narray into adjacent kmalloc-1k slab bytes. hwrng_fillfn() mixes\nthose bytes into the guest RNG, and guest root can also observe\nthem directly via /dev/hwrng.\n\nConcrete impact is inside the guest:\n\n - Memory-safety / hardening: any virtio-rng backend that\n over-reports used.len causes the driver to read past vi->data\n into unrelated slab contents. hwrng_fillfn() is a kernel thread\n that runs as soon as the device is probed; no guest userspace\n interaction is required to first-trigger the OOB.\n\n - Cross-boundary leak (confidential-compute threat model): a\n malicious hypervisor cooperating with a malicious or compromised\n guest root userspace can use /dev/hwrng as a leak channel for\n guest-kernel heap data. The host sets a large used.len, guest\n root reads /dev/hwrng, and the returned bytes contain guest\n kernel slab contents that were adjacent to vi->data. In\n practice, confidential-compute guests (SEV-SNP, TDX) usually\n disable virtio-rng entirely, so this path is narrow, but the\n fix is still worth carrying because the underlying\n memory-safety bug contaminates the guest RNG on any host.\n\nKASAN confirms the OOB on a 7.1-rc4 guest whose virtio-rng backend\nhas been patched to report used.len = 0x10000:\n\n BUG: KASAN: slab-out-of-bounds in virtio_read+0x394/0x5d0\n Read of size 64 at addr ffff88800ae0ba20 by task hwrng/52\n Call Trace:\n __asan_memcpy+0x23/0x60\n virtio_read+0x394/0x5d0\n hwrng_fillfn+0xb2/0x470\n kthread+0x2cc/0x3a0\n Allocated by task 1:\n probe_common+0xa5/0x660\n virtio_dev_probe+0x549/0xbc0\n The buggy address belongs to the object at ffff88800ae0b800\n which belongs to the cache kmalloc-1k of size 1024\n The buggy address is located 0 bytes to the right of\n allocated 544-byte region [ffff88800ae0b800, ffff88800ae0ba20)\n\nSame class of bug as commit c04db81cd028 (\"net/9p: Fix buffer\noverflow in USB transport layer\"), which hardened\nusb9pfs_rx_complete() against unchecked device-reported length in\nthe USB 9p transport.\n\nWith the clamp at point of use and array_index_nospec() in place,\nthe same harness boots cleanly: copy_data() returns zero for the\nbogus report, the device-supplied bytes after data_idx are\ndiscarded, and the driver issues a fresh request." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "baseScore": 7.7, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The attacker must control a virtio-rng backend or hypervisor locally attached to the guest; no network or physical packet path reaches this driver.\nAC:L - The backend directly controls the 32-bit used.len and can deterministically over-report it without winning a race or manipulating an uncertain memory layout.\nPR:N - No privileges inside the vulnerable guest are required because the hwrng kernel thread automatically consumes backend completions after device registration.\nUI:N - The automatically started hwrng thread triggers the out-of-bounds read without any victim action or guest userspace request.\nS:U - The vulnerable driver and the affected memory, RNG state, and availability all belong to the same guest-kernel security authority; this is not a guest-to-host escape.\nC:H - Repeated bounded copies advance through a device-selected, potentially enormous length, producing sequential out-of-bounds reads of guest-kernel heap memory that guest root can observe through /dev/hwrng.\nI:N - The memcpy destination remains bounded by the hwrng core buffer, so the flaw provides no out-of-bounds write, use-after-free, or control-flow modification primitive.\nA:H - A sufficiently large reported length drives reads beyond valid slab memory, causing a kernel out-of-bounds fault, oops, or panic, and the malicious backend can trigger it repeatedly." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/char/hw_random/virtio-rng.c" ], "versions": [ { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "3aa3e89cf80721c8d382b4c1a2b70a0449dad4a5", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "63335e7b638ae70028ae285bb95153874a8bc852", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "2e788948ff2a13358a303af112497a63201c5739", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "fde19b0d4eeabae042519313c843fe6f27d41e9d", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "81dd21b5f0c299cc7b5bf84f04a61938559d20e6", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "285e17c44e3873a73460f294acbd64018ff64385", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "92d5736a62040ec1cfff23ea57e6599301690ad5", "status": "affected", "versionType": "git" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "lessThan": "e3046eeada299f917a8ad883af4434bfb86556b1", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "drivers/char/hw_random/virtio-rng.c" ], "versions": [ { "version": "2.6.26", "status": "affected" }, { "version": "0", "lessThan": "2.6.26", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.261", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.212", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.96", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.39", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.4", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "5.10.261" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "5.15.212" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "6.12.96" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "6.18.39" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "7.1.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.26", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/3aa3e89cf80721c8d382b4c1a2b70a0449dad4a5" }, { "url": "https://git.kernel.org/stable/c/63335e7b638ae70028ae285bb95153874a8bc852" }, { "url": "https://git.kernel.org/stable/c/2e788948ff2a13358a303af112497a63201c5739" }, { "url": "https://git.kernel.org/stable/c/fde19b0d4eeabae042519313c843fe6f27d41e9d" }, { "url": "https://git.kernel.org/stable/c/81dd21b5f0c299cc7b5bf84f04a61938559d20e6" }, { "url": "https://git.kernel.org/stable/c/285e17c44e3873a73460f294acbd64018ff64385" }, { "url": "https://git.kernel.org/stable/c/92d5736a62040ec1cfff23ea57e6599301690ad5" }, { "url": "https://git.kernel.org/stable/c/e3046eeada299f917a8ad883af4434bfb86556b1" } ], "title": "hwrng: virtio: clamp device-reported used.len at copy_data()", "x_generator": { "engine": "bippy-1.2.0" } } } }