CVE-2026-89927Public exploit

Host CPU livelock via synthetic timer overflow

Published Sep 16, 2026 · Updated Sep 16, 2026

Integer overflow in Linux KVM Hyper-V synthetic timers allows guest OS users or local userspace to cause a host CPU livelock. stimer_start() multiplies an attacker-controlled 100-nanosecond COUNT delta by 100 without overflow protection, then arms an hrtimer with the wrapped deadline in the past. A guest WRMSR or host KVM_SET_MSRS call can trigger repeated immediate timer rearming, preventing vCPU progress and starving RCU grace-period threads.

CVSS severityUnavailable
Unscored
EPSS probabilityUnavailable
No score available in this record
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Integer overflow in Linux KVM Hyper-V synthetic timers allows guest OS users or local userspace to cause a host CPU livelock. stimer_start() multiplies an attacker-controlled 100-nanosecond COUNT delta by 100 without overflow protection, then arms an hrtimer with the wrapped deadline in the past. A guest WRMSR or host KVM_SET_MSRS call can trigger repeated immediate timer rearming, preventing vCPU progress and starving RCU grace-period threads.

The record

CVE
CVE-2026-89927
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499.004
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Sep 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <0ca49fbd2883cd53d32d85b50feef17fa04d0fbf
  2. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <3097582b73a8ed1cd6f6790fa78706f4a79b5a49
  3. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <61954727ee08f026f5e1c9ee69e1b404a68f2f7a
  4. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <6a8ba9213cce613455b1502ee0fd178656bf617b
  5. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <8aa467fe757d8cb2278e98d7fbf44fc05eb0dbf8
  6. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <8e19ded84336891646b31375720717635f0fdd90
  7. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <a4665762388750e08df99baabe5fce2a21d1423e
  8. Affected versionversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <bdb732ebee545b7e3bee7060efc754a8d99818b9
  9. Affected versionversion=4.5

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=1f4b34f825e8cef6f493d06b46605384785b3d16 <0ca49fbd2883cd53d32d85b50feef17fa04d0fbf; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <3097582b73a8ed1cd6f6790fa78706f4a79b5a49; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <61954727ee08f026f5e1c9ee69e1b404a68f2f7a; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <6a8ba9213cce613455b1502ee0fd178656bf617b; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <8aa467fe757d8cb2278e98d7fbf44fc05eb0dbf8; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <8e19ded84336891646b31375720717635f0fdd90; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <a4665762388750e08df99baabe5fce2a21d1423e; version=1f4b34f825e8cef6f493d06b46605384785b3d16 <bdb732ebee545b7e3bee7060efc754a8d99818b9; version=4.5

Published CVSS scores

No CVSS assessment is available in this record.

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo