{ "affected": [ { "ranges": [ { "events": [ { "introduced": "f7f510ec195781c857ab76366a3e1c59e1caae42" }, { "fixed": "3aa3e89cf80721c8d382b4c1a2b70a0449dad4a5" }, { "fixed": "63335e7b638ae70028ae285bb95153874a8bc852" }, { "fixed": "2e788948ff2a13358a303af112497a63201c5739" }, { "fixed": "fde19b0d4eeabae042519313c843fe6f27d41e9d" }, { "fixed": "81dd21b5f0c299cc7b5bf84f04a61938559d20e6" }, { "fixed": "285e17c44e3873a73460f294acbd64018ff64385" }, { "fixed": "92d5736a62040ec1cfff23ea57e6599301690ad5" }, { "fixed": "e3046eeada299f917a8ad883af4434bfb86556b1" } ], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "type": "GIT" } ] }, { "package": { "ecosystem": "Linux", "name": "Kernel" }, "ranges": [ { "events": [ { "introduced": "2.6.26" }, { "fixed": "5.10.261" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.11.0" }, { "fixed": "5.15.212" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "5.16.0" }, { "fixed": "6.1.178" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.2.0" }, { "fixed": "6.6.145" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.7.0" }, { "fixed": "6.12.96" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.13.0" }, { "fixed": "6.18.39" } ], "type": "ECOSYSTEM" }, { "events": [ { "introduced": "6.19.0" }, { "fixed": "7.1.4" } ], "type": "ECOSYSTEM" } ] } ], "database_specific": { "cna_assigner": "Linux", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64456.json" }, "details": "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-\u003edata_avail. copy_data() then indexes vi-\u003edata[] using\nvi-\u003edata_idx (advanced by previous copy_data() calls) and issues a\nmemcpy() without re-validating either value against the posted\nbuffer size sizeof(vi-\u003edata) (SMP_CACHE_BYTES bytes, typically 32\nor 64).\n\nA malicious or buggy virtio-rng backend can set used.len beyond\nsizeof(vi-\u003edata), 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-\u003edata\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-\u003edata. 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.", "id": "CVE-2026-64456", "modified": "2026-07-28T03:55:40.669310862Z", "published": "2026-07-25T08:51:24.659Z", "references": [ { "type": "WEB", "url": "https://git.kernel.org/stable/c/285e17c44e3873a73460f294acbd64018ff64385" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/2e788948ff2a13358a303af112497a63201c5739" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/3aa3e89cf80721c8d382b4c1a2b70a0449dad4a5" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/63335e7b638ae70028ae285bb95153874a8bc852" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/81dd21b5f0c299cc7b5bf84f04a61938559d20e6" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/92d5736a62040ec1cfff23ea57e6599301690ad5" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/e3046eeada299f917a8ad883af4434bfb86556b1" }, { "type": "WEB", "url": "https://git.kernel.org/stable/c/fde19b0d4eeabae042519313c843fe6f27d41e9d" }, { "type": "ADVISORY", "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64456.json" }, { "type": "ADVISORY", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64456" }, { "type": "PACKAGE", "url": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git" } ], "schema_version": "1.8.0", "severity": [ { "score": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "type": "CVSS_V3" } ], "summary": "hwrng: virtio: clamp device-reported used.len at copy_data()" }