hwrng: virtio: clamp device-reported used.len at copy_data()
In the Linux kernel, the following vulnerability has been resolved: hwrng: virtio: clamp device-reported used.len at copy_data() random_recv_done() stores the device-reported used.len directly into vi->data_avail. copy_data() then indexes vi->data[] using vi->data_idx (advanced by previous copy_data() calls) and issues a memcpy() without re-validating either value against the posted buffer size sizeof(vi->data) (SMP_CACHE_BYTES bytes, typically 32 or 64). A malicious or buggy virtio-rng backend can set used.len beyond sizeof(vi->data), steering the memcpy() past the end of the inline array into adjacent kmalloc-1k slab bytes. hwrng_fillfn() mixes those bytes into the guest RNG, and guest root can also observe them directly via /dev/hwrng. Concrete impact is inside the guest: - Memory-safety / hardening: any virtio-rng backend that over-reports used.len causes the driver to read past vi->data into unrelated slab contents. hwrng_fillfn() is a kernel thread that runs as soon as the device is probed; no guest userspace interaction is required to first-trigger the OOB. - Cross-boundary leak (confidential-compute threat model): a malicious hypervisor cooperating with a malicious or compromised guest root userspace can use /dev/hwrng as a leak channel for guest-kernel heap data. The host sets a large used.len, guest root reads /dev/hwrng, and the returned bytes contain guest kernel slab contents that were adjacent to vi->data. In practice, confidential-compute guests (SEV-SNP, TDX)
CVE-2026-64456
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-64456
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "3aa3e89cf80721c8d382b4c1a2b70a0449dad4a5",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "63335e7b638ae70028ae285bb95153874a8bc852",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "2e788948ff2a13358a303af112497a63201c5739",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "fde19b0d4eeabae042519313c843fe6f27d41e9d",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "81dd21b5f0c299cc7b5bf84f04a61938559d20e6",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "285e17c44e3873a73460f294acbd64018ff64385",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "92d5736a62040ec1cfff23ea57e6599301690ad5",
"versionType": "git"
},
{
"status": "affected",
"version": "f7f510ec195781c857ab76366a3e1c59e1caae42",
"lessThan": "e3046eeada299f917a8ad883af4434bfb86556b1",
"versionType": "git"
}
],
"programFiles": [
"drivers/char/hw_random/virtio-rng.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.26"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.26",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.261",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.145",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.96",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.39",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.4",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"drivers/char/hw_random/virtio-rng.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-64456
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #41054 · Revision 1
- Added to Heist Feed
- Publisher date