VulnerabilityPublished 16 Sep 2026Updated 5 Oct 2026

CVE-2026-89981: Linux kernel · arm64: Don't read GMID_EL1 when MTE is disabled

Affects Linux kernelSource GCVE Database

Not known to be exploited.

Data as of 26 Oct 2026, 14:05 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that gates the GMID_EL1 register read based on CPU features and kernel configuration. Users should update to patched kernel versions that include this fix. No additional mitigations are indicated by the vendor advisory.

Description

A vulnerability in the Linux kernel arm64 architecture was resolved that involved reading the GMID_EL1 register even when Memory Tagging Extension (MTE) is disabled. This could cause an undefined instruction exception and kernel panic in pKVM environments when CPUs are offlined and brought back online. The fix gates the GMID_EL1 read based on CPU features and configuration to prevent this error.

Impact

This vulnerability causes a kernel panic and undefined instruction exception in pKVM environments on arm64 systems when CPUs are offlined and brought back online. It affects system stability and availability in these specific configurations but does not indicate broader compromise or data loss.

Summary

The Linux kernel arm64 vulnerability (CVE-2026-89981) occurs because __cpuinfo_store_cpu() reads the GMID_EL1 register without properly checking if MTE is enabled. When MTE is disabled (CONFIG_ARM64_MTE=n or arm64.nomte), KVM sets HCR_EL2.TID5, and pKVM triggers an undefined instruction exception leading to a kernel panic during CPU offline/online cycles. The fix involves gating the GMID_EL1 read on the CPU's own ID_AA64PFR1_EL1 register and the kernel configuration to avoid reading this register when MTE is disabled, preventing the panic.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 24 Oct 2026, 20:37 UTC

Technical details

References

Community reviews

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