KVM: Replace guest-triggerable BUG_ON() in ioeventfd datamatch with get_unaligned()
In the Linux kernel, the following vulnerability has been resolved: KVM: Replace guest-triggerable BUG_ON() in ioeventfd datamatch with get_unaligned() Drop a BUG_ON() that has been reachable since it was first added, way back in 2009, and instead use get_unaligned() to perform potentially-unaligned accesses. For a given store, KVM x86's emulator tracks the entire value in the destination operand, x86_emulate_ctxt.dst. If the destination is memory, and the target splits multiple pages and/or is emulated MMIO, then KVM handles each fragment independently. E.g. on a page split starting at page offset 0xffc, KVM writes 4 bytes to the first page, then the remaining bytes to the second page, using ctxt->dst as the source for both (with appropriate offsets). If the destination splits a page *and* hits emulated MMIO on the second page, then KVM will complete the write to the first page, then emulate the MMIO access to the second page. If there is a datamatch-enabled ioeventfd at offset 0 of the second page, then KVM will process the remainder of the store as a potential ioeventfd signal. Putting it all together, if the guest emits a store that splits a page starting at page offset N, and the second page has a datamatch-enabled ioeventfd at offset 0, then KVM will check for datamatch using &dst.valptr[N] as the source. Due to dst (and thus dst.valptr) being 32-byte aligned, if N is not aligned to @len, the BUG_ON() fires. E.g. with a 16-byte store at page offset 0xffc, to an ioeventf
CVE-2026-63806
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-2026-63806
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": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "2426c15c1395b7d5ccf1e5025ca898af7f3decb6",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "4186c850789906b875a1d263377a4d37c078e317",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "36ff44fb3d89960391e013fb9d91e23dbc48be47",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "92fc631b69deb1c7d56aec2663003600799dcd75",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "bf89e3738480d33cd515b4a18900e8443d40cd2e",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "5da9b1a87ec7cc3489c27016313524769f12d9e0",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "5c87b47374682f69686068ad0a7779365a527b1c",
"versionType": "git"
},
{
"status": "affected",
"version": "d34e6b175e61821026893ec5298cc8e7558df43a",
"lessThan": "f1edbed787ba67988ed34e0132ca128b052b6ce8",
"versionType": "git"
}
],
"programFiles": [
"virt/kvm/eventfd.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.32"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "2.6.32",
"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": "6.12.95",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"virt/kvm/eventfd.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-63806
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #40834 · Revision 1
- Added to Heist Feed
- Publisher date