Linux Kernel up to 6.18.50/7.2.4 KVM invalidate_vncr_va toctou

CVSS Meta Temp Score
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CTI Interest Score
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9.5$0-$5k0.00-

Summaryinfo

A vulnerability described as very critical has been identified in Linux Kernel up to 6.18.50/7.2.4. This vulnerability affects the function invalidate_vncr_va of the component KVM. Executing a manipulation can lead to toctou. This vulnerability is registered as CVE-2026-89916. It is possible to launch the attack remotely. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability has been found in Linux Kernel up to 6.18.50/7.2.4 and classified as very critical. This vulnerability affects the function invalidate_vncr_va of the component KVM. The manipulation with an unknown input leads to a toctou vulnerability. The CWE definition for the vulnerability is CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Make VNCR invalidation participate in MMU invalidation retry A VNCR TLB invalidation can occur on one vcpu while another vcpu is faulting in this same page. Without correctly handling this, we can end up with the following scenario: - vcpu A walks the PTs to translate VNCR - before vcpu A is able to grab the MMU lock to insert the TLB, vcpu B updates the S1 PTs with an invalid entry, and issues a TLBI S1E2 for this VA - vcpu A inserts the TLB for something that is now invalid This isn't a new problem, and we manage S2 by having the MMU notifier to bump up mmu_invalidate_seq on invalidation so that the fault can be replayed. We can perform something similar here, and extend invalidate_vncr_va() to update the same counter, clearly indicating that the context has changed under our feet. This is safe as the invalidation always happen while holding the MMU lock for write, and that we sample the sequence number before walking S1.

The advisory is shared for download at git.kernel.org. This vulnerability was named CVE-2026-89916 since 09/11/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 09/16/2026).

Upgrading to version 6.18.51, 7.2.5 or 7.3-rc1 eliminates this vulnerability. Applying the patch d8580e7aa189b0c6c5bb4d94b8352728a7c35bbd/11ee3faab4f1755d126bead9f882e75a7a677860/2b7324f3a0c1072b9d578b8d42f199506753f26e is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.9
VulDB Meta Temp Score: 9.5

VulDB Base Score: 9.9
VulDB Temp Score: 9.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Toctou
CWE: CWE-367 / CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.51/7.2.5/7.3-rc1
Patch: d8580e7aa189b0c6c5bb4d94b8352728a7c35bbd/11ee3faab4f1755d126bead9f882e75a7a677860/2b7324f3a0c1072b9d578b8d42f199506753f26e

Timelineinfo

09/11/2026 CVE reserved
09/16/2026 +5 days Advisory disclosed
09/16/2026 +0 days VulDB entry created
09/16/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-89916 (🔒)
GCVE (CVE): GCVE-0-2026-89916
GCVE (VulDB): GCVE-100-405760

Entryinfo

Created: 09/16/2026 14:40
Changes: 09/16/2026 14:40 (59)
Complete: 🔍
Cache ID: 216::103

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