{ "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-2026-64456", "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-64456", "idYear": 2026, "status": "PUBLISHED", "publishedAt": "2026-07-25T08:51:24.659Z", "updatedAt": "2026-10-19T20:38:30.595Z", "importedAt": "2026-10-24T01:58:25.636Z", "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": "hwrng: virtio: clamp device-reported used.len at copy_data()", "summary": "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.", "affected": [ { "vendor": "Linux", "product": "Linux", "defaultStatus": "unaffected", "versions": [ { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "3aa3e89cf80721c8d382b4c1a2b70a0449dad4a5" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "63335e7b638ae70028ae285bb95153874a8bc852" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "2e788948ff2a13358a303af112497a63201c5739" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "fde19b0d4eeabae042519313c843fe6f27d41e9d" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "81dd21b5f0c299cc7b5bf84f04a61938559d20e6" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "285e17c44e3873a73460f294acbd64018ff64385" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "92d5736a62040ec1cfff23ea57e6599301690ad5" }, { "version": "f7f510ec195781c857ab76366a3e1c59e1caae42", "status": "affected", "versionType": "git", "lessThan": "e3046eeada299f917a8ad883af4434bfb86556b1" } ] }, { "vendor": "Linux", "product": "Linux", "defaultStatus": "affected", "versions": [ { "version": "2.6.26", "status": "affected" }, { "version": "0", "status": "unaffected", "versionType": "semver", "lessThan": "2.6.26" }, { "version": "5.10.261", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.10.*" }, { "version": "5.15.212", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "5.15.*" }, { "version": "6.1.178", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.1.*" }, { "version": "6.6.145", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.6.*" }, { "version": "6.12.96", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.12.*" }, { "version": "6.18.39", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "6.18.*" }, { "version": "7.1.4", "status": "unaffected", "versionType": "semver", "lessThanOrEqual": "7.1.*" }, { "version": "7.2", "status": "unaffected", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*" } ] } ] } } }