EUVD-2026-66470
GHSA-w6fw-g579-ffcw
Severity by source
AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
PR:L applied because guest-level access to an assigned vfio_ccw device is a prerequisite; PR:N overstates universality of access within a guest.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
s390/vfio_ccw: Free all memory if cp_init() fails
The routine cp_free() is called to unpin/free any memory once an I/O is completed successfully, or if cp_prefetch() fails. But if cp_init() fails, and cp->initialized is not enabled, the same routine cannot be used to free all the memory.
An attempt to address this exists in ccwchain_handle_ccw(), where a single call to ccwchain_free() is made for the currently-processed CCW segment. But this will leak other segments (created as a result of a Transfer in Channel) that had been allocated as part of the same channel program.
Address this by performing the cleanup outside of the recursive ccwchain_handle_ccw()/ccwchain_loop_tic() logic.
AnalysisAI
Memory leak in the Linux kernel s390/vfio_ccw subsystem enables a guest VM user to exhaust host kernel memory by submitting crafted channel programs that trigger cp_init() failure paths, leaving ccwchain segments unfreed. Affected deployments are IBM s390 (mainframe) KVM hosts that have vfio channel command word (CCW) device passthrough configured, making the attack surface highly specific. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) an IBM s390 (mainframe) architecture host running KVM, (2) at least one channel I/O device configured for vfio_ccw passthrough to a guest VM, and (3) guest-level access sufficient to submit channel programs through the vfio_ccw interface - no elevated privileges within the guest are required if the guest user has default device access. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Real-world risk is low-to-moderate despite the 7.1 CVSS score due to several strong limiting factors. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the vendor-released kernel patch corresponding to the active stable branch: upgrade to Linux 6.12.105, 6.18.46, 7.1.10, or 7.2, available via kernel.org stable trees and distribution security channels. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all IBM s390 KVM hosts in production with vfio-ccw device passthrough enabled and assess current guest isolation policies. …
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External POC / Exploit Code
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