VulnerabilityPublished 16 Sep 2026Updated 30 Oct 2026

CVE-2026-89958: Linux kernel · s390/vfio-ap: Fix dereference matrix_mdev->kvm without checking for NULL

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in d50346801b4f144e42b49cd4f1496010498ab114 : update Linux kernel when convenient.

Data as of 30 Oct 2026, 13:03 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in d50346801b4f144e42b49cd4f1496010498ab114, 334b435b951353f934d5110c4630e0cb58d2f9a7, 178ea7a1c2c3c0c01d14b8f60aa35f1e0cdc6b78 +3

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, < d50346801b4f144e42b49cd4f1496010498ab114	Fixed in d50346801b4f144e42b49cd4f1496010498ab114
LinuxLinux	Affected ≥ eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, < 334b435b951353f934d5110c4630e0cb58d2f9a7	Fixed in 334b435b951353f934d5110c4630e0cb58d2f9a7
LinuxLinux	Affected ≥ eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, < 178ea7a1c2c3c0c01d14b8f60aa35f1e0cdc6b78	Fixed in 178ea7a1c2c3c0c01d14b8f60aa35f1e0cdc6b78
LinuxLinux	Affected ≥ eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, < 5e932abfcce6189d067fffb0eb8214443bc04374	Fixed in 5e932abfcce6189d067fffb0eb8214443bc04374
LinuxLinux	Affected ≥ eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, < 4f7e869d0db24ae07b4c888fd3bc21554eef775d	Fixed in 4f7e869d0db24ae07b4c888fd3bc21554eef775d
LinuxLinux	Affected ≥ eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, < 2fbe430fe40bc5adb7e439d0136d2c5fe34613ba	Fixed in 2fbe430fe40bc5adb7e439d0136d2c5fe34613ba

AI-suggested

A patch is available and has been applied in the Linux kernel source. Users and administrators should update to a fixed kernel version that includes the commits referenced in the fix. Since this is a kernel-level issue, applying the official kernel update is the recommended remediation. No additional mitigations are indicated or required.

Description

CVE-2026-89958 is a vulnerability in the Linux kernel's s390 vfio-ap driver where a NULL pointer dereference can occur due to missing checks before accessing matrix_mdev->kvm. This flaw arises when the code attempts to take a mutex lock on matrix_mdev->kvm->lock without verifying if matrix_mdev->kvm is NULL. The issue has been fixed by adding proper NULL checks before accessing the kvm lock. The vulnerability affects Linux kernel version 6.0 and has been patched in subsequent commits.

Impact

The vulnerability can cause a NULL pointer dereference in the Linux kernel, leading to a kernel crash or denial of service on affected systems running the s390 vfio-ap driver. There is no indication of code execution or privilege escalation from the provided data. The impact is limited to stability and availability of the affected kernel subsystem.

Summary

The Linux kernel s390 vfio-ap driver implements two callback functions, vfio_ap_on_cfg_changed and vfio_ap_on_scan_complete, which access matrix_mdev->kvm->lock mutex without checking if matrix_mdev->kvm is NULL. If matrix_mdev->kvm is unset, dereferencing it causes a NULL pointer dereference, potentially leading to kernel crashes. The fix involves adding checks for matrix_mdev->kvm being NULL before taking the kvm lock mutex and rearranging lock acquisition order to prevent lock dependency issues. The patch ensures safe access to matrix_mdev fields and proper synchronization during AP device configuration changes.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 13:03 UTC

Technical details

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