KVM: x86: hyper-v: Clamp stimer deadline to avoid livelock
In the Linux kernel, the following vulnerability has been resolved: KVM: x86: hyper-v: Clamp stimer deadline to avoid livelock Fix an issue where userspace or the guest can program an Hyper-V synthetic timer to have a deadline in the past via integer overflow, preventing the CPU from making progress and triggering an RCU stall. Hyper-V's SynIC exposes 4 per-vCPU synthetic timers to the guest, which are emulated by KVM. Each is programmed through the HV_X64_MSR_STIMERi_CONFIG and HV_X64_MSR_STIMERi_COUNT MSRs. Depending on CONFIG, COUNT represents either the absolute expiration time or the period of a periodic timer, both expressed in 100ns ticks. These timers may be set both by the guest (WRMSR) and the host (KVM_SET_MSRS). When the timer is enabled, stimer_start() translates COUNT to an absolute monotonic deadline and arms an hrtimer. If COUNT is set to a value close to U64_MAX, the deadline calculation can overflow. ktime_add_ns(ktime_now, 100 * (stimer->exp_time - time_now)) This can result in a CPU livelock. stimer_start() arms the timer via hrtimer_start() with a deadline in the past, which causes it to immediately fire. The stimer callback then raises KVM_RQ_HV_STIMER, with the intention of causing KVM to deliver a synthetic interrupt on the next vCPU guest enter. Then, once userspace issues KVM_RUN, vcpu_enter_guest() consumes the request, calling kvm_hv_process_stimers(). This would normally disable the timer via stimer_expiration() once the deadline is in the past. H
CVE-2026-89927
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-2026-89927
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": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "a4665762388750e08df99baabe5fce2a21d1423e",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "61954727ee08f026f5e1c9ee69e1b404a68f2f7a",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "8aa467fe757d8cb2278e98d7fbf44fc05eb0dbf8",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "8e19ded84336891646b31375720717635f0fdd90",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "6a8ba9213cce613455b1502ee0fd178656bf617b",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "3097582b73a8ed1cd6f6790fa78706f4a79b5a49",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "bdb732ebee545b7e3bee7060efc754a8d99818b9",
"versionType": "git"
},
{
"status": "affected",
"version": "1f4b34f825e8cef6f493d06b46605384785b3d16",
"lessThan": "0ca49fbd2883cd53d32d85b50feef17fa04d0fbf",
"versionType": "git"
}
],
"programFiles": [
"arch/x86/kvm/hyperv.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.5"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.5",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.270",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.221",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.188",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.110",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.51",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.5",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"arch/x86/kvm/hyperv.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89927
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #36369 · Revision 1
- Added to Heist Feed
- Publisher date