CVE-2026-80921

Cross-tenant crypto access via stale APCB bits

Published Sep 9, 2026 · Updated Sep 10, 2026

Access-control failure in Linux KVM for s390 allows local users to access cryptographic devices outside their delegated matrix. The setup_apcb10() path copies only bits 0–63 from a format-0 or format-1 access-control block, leaving bits 64–255 from a reused vsie page intact. An L1 guest with supervisor access must run nested virtualization and reuse the page; stale bits then let its nested guest read, alter, or disrupt queues belonging to the host or another guest.

CVSS severity8.8
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Access-control failure in Linux KVM for s390 allows local users to access cryptographic devices outside their delegated matrix. The setup_apcb10() path copies only bits 0–63 from a format-0 or format-1 access-control block, leaving bits 64–255 from a reused vsie page intact. An L1 guest with supervisor access must run nested virtualization and reuse the page; stale bits then let its nested guest read, alter, or disrupt queues belonging to the host or another guest.

The record

CVE
CVE-2026-80921
Published
Sep 9, 2026
Updated
Sep 10, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 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=4.20
  2. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <087c19cc60a8caa1a08e1e434c8be2caf6c27733
  3. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <29b4f7bc2991313bd3e6f6fb8fdf1b173f086dd6
  4. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <34d5b5b646c91cfb9338d7a12c955a70ffb8c66b
  5. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <59d51550b5cb916bda037673a721a404b3b47a0d
  6. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <7d23489f51109e3ebba5b5db8c5f0185af7b7fdf
  7. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <935eeba276012916c76243e5cbb843efd8fdb75d
  8. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <d110b3297f11ef227098b8a82ade2d5f123b7d2f
  9. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <d4bcd2df6d0d2af916b4fe1a533958778ea7c45b
  10. Affected versionversion=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <f6079dca67eccb5eabef9f72437948c66dc5131f

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=4.20; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <087c19cc60a8caa1a08e1e434c8be2caf6c27733; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <29b4f7bc2991313bd3e6f6fb8fdf1b173f086dd6; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <34d5b5b646c91cfb9338d7a12c955a70ffb8c66b; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <59d51550b5cb916bda037673a721a404b3b47a0d; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <7d23489f51109e3ebba5b5db8c5f0185af7b7fdf; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <935eeba276012916c76243e5cbb843efd8fdb75d; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <d110b3297f11ef227098b8a82ade2d5f123b7d2f; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <d4bcd2df6d0d2af916b4fe1a533958778ea7c45b; version=6b79de4b056e5a2febc0c61233d8f0ad7868e49c <f6079dca67eccb5eabef9f72437948c66dc5131f

Published CVSS scores

8.8Linux CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

No sourced classifications are available.

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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