CVE-2026-89903

CPU hard lock via stale per-CPU base restoration

Published Sep 16, 2026 · Updated Sep 16, 2026

A rethook trampoline flaw in Linux on LoongArch allows attackers to hard-lock CPUs under kretprobe-heavy preemptible load. The trampoline restores an $r21 per-CPU base saved before rethook_trampoline_handler() can schedule, so migration makes later this_cpu_*() accesses use the previous CPU's data. Triggering requires kretprobes, preemption, migration, and sustained workload; the resulting scheduler and timer corruption can leave CPUs parked without rearming the timer.

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

What happened

A rethook trampoline flaw in Linux on LoongArch allows attackers to hard-lock CPUs under kretprobe-heavy preemptible load. The trampoline restores an $r21 per-CPU base saved before rethook_trampoline_handler() can schedule, so migration makes later this_cpu_*() accesses use the previous CPU's data. Triggering requires kretprobes, preemption, migration, and sustained workload; the resulting scheduler and timer corruption can leave CPUs parked without rearming the timer.

The record

CVE
CVE-2026-89903
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
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

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Is a vulnerable build present?

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

  1. Affected versionversion=3f5536860086d906b01ec5ed68cf50c7edcc40af <266ffc92e68593759adfe3d58f188773d32782c3
  2. Affected versionversion=3f5536860086d906b01ec5ed68cf50c7edcc40af <8f15e95b438bc6b3c9f23a33c9a0d0678ebd1dc8
  3. Affected versionversion=3f5536860086d906b01ec5ed68cf50c7edcc40af <a03b5e7483ad2c33ba5dd2adb8552e84bfee8fe2
  4. Affected versionversion=3f5536860086d906b01ec5ed68cf50c7edcc40af <c048b0a3c0836c4b1bef4b51d355d27090bf6790
  5. Affected versionversion=3f5536860086d906b01ec5ed68cf50c7edcc40af <c3f2feace5e4f4b01b68b9f947b19adb4155c32e
  6. Affected versionversion=6.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=3f5536860086d906b01ec5ed68cf50c7edcc40af <266ffc92e68593759adfe3d58f188773d32782c3; version=3f5536860086d906b01ec5ed68cf50c7edcc40af <8f15e95b438bc6b3c9f23a33c9a0d0678ebd1dc8; version=3f5536860086d906b01ec5ed68cf50c7edcc40af <a03b5e7483ad2c33ba5dd2adb8552e84bfee8fe2; version=3f5536860086d906b01ec5ed68cf50c7edcc40af <c048b0a3c0836c4b1bef4b51d355d27090bf6790; version=3f5536860086d906b01ec5ed68cf50c7edcc40af <c3f2feace5e4f4b01b68b9f947b19adb4155c32e; version=6.3

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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

Technologies

Your stack

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Your stack

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