CVE-2026-80550

Host kernel-memory disclosure via CCW over-read

Published Aug 26, 2026 · Updated Aug 27, 2026

An out-of-bounds read in affected Linux kernel builds allows guest OS users to expose adjacent host kernel heap memory. The ccwchain_calc_length() loop examines a 257th struct ccw1 after processing the 256-entry guest_cp array instead of stopping at index 255. Reachability requires an IBM Z or LinuxONE KVM guest with an assigned vfio-ccw mediated subchannel; the flaw performs no out-of-bounds write, and only hardened builds are expected to fault.

CVSS severity7.9
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

An out-of-bounds read in affected Linux kernel builds allows guest OS users to expose adjacent host kernel heap memory. The ccwchain_calc_length() loop examines a 257th struct ccw1 after processing the 256-entry guest_cp array instead of stopping at index 255. Reachability requires an IBM Z or LinuxONE KVM guest with an assigned vfio-ccw mediated subchannel; the flaw performs no out-of-bounds write, and only hardened builds are expected to fault.

The record

CVE
CVE-2026-80550
Published
Aug 26, 2026
Updated
Aug 27, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
Unavailable
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 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=0a19e61e6d4c6192077ead760ba0a2d350987d4c <0282fb1c4b638eecfe2cc558092c460911d8f7e2
  2. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <499a8a66b1598bfab97182aed15e0f1646074a3d
  3. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <4c2e1d359d7a2b82cdf3254e4e480af9417f99fb
  4. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <907adc667d902fafbdb2d740d57b55bd025dc4cd
  5. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <a005b7f1a491ffda61bff0fd0f6548f8986fb977
  6. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <af3f80ca4c8b17f20f9e588def076288fdb49e65
  7. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <d5d096cd9369e986d4e5153baa86b8b35c283e09
  8. Affected versionversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3
  9. Affected versionversion=4.12

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=0a19e61e6d4c6192077ead760ba0a2d350987d4c <0282fb1c4b638eecfe2cc558092c460911d8f7e2; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <499a8a66b1598bfab97182aed15e0f1646074a3d; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <4c2e1d359d7a2b82cdf3254e4e480af9417f99fb; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <907adc667d902fafbdb2d740d57b55bd025dc4cd; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <a005b7f1a491ffda61bff0fd0f6548f8986fb977; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <af3f80ca4c8b17f20f9e588def076288fdb49e65; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <d5d096cd9369e986d4e5153baa86b8b35c283e09; version=0a19e61e6d4c6192077ead760ba0a2d350987d4c <f20be33d093ce7630c17ff7ed93caf7eaf8ac1a3; version=4.12

Published CVSS scores

7.9Linux Kernel CVE TeamCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:L

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesunauthenticated
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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