EUVD-2026-39841
GHSA-v222-hvcr-rghc
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Local-only kernel driver path (AV:L), low-privilege trigger (PR:L), no confidentiality or integrity impact, kernel panic yields high availability loss.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
tty: hvc_iucv: fix off-by-one in number of supported devices
MAX_HVC_IUCV_LINES HVC_ALLOC_TTY_ADAPTERS 8. This is the number of entries in: static struct hvc_iucv_private *hvc_iucv_table[MAX_HVC_IUCV_LINES];
Sometimes hvc_iucv_table[] is limited by: (a) if (num > hvc_iucv_devices) // for error detection or (b) for (i = 0; i < hvc_iucv_devices; i++) // in 2 places (so these 2 don't agree; second one appears to be correct to me.)
hvc_iucv_devices can be 0..8. This is a counter. (c) if (hvc_iucv_devices > MAX_HVC_IUCV_LINES)
If hvc_iucv_devices == 8, (a) allows the code to access hvc_iucv_table[8]. Oops.
AnalysisAI
Off-by-one array overflow in the Linux kernel's hvc_iucv driver (IBM z/VM IUCV HVC terminal subsystem) can trigger an out-of-bounds write to hvc_iucv_table[8] when hvc_iucv_devices is set to the maximum value of 8, crashing the kernel. Exploitation requires local access with low privileges on IBM System z systems running z/VM with hvc_iucv configured. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) an IBM System z system running z/VM with the hvc_iucv kernel driver loaded (exclusive to mainframe environments - this driver does not exist on any other architecture); (2) hvc_iucv_devices configured to exactly 8 (the maximum, MAX_HVC_IUCV_LINES), which may be a default maximum or an explicitly set module/boot parameter; (3) local system access with at minimum low privileges (PR:L per CVSS vector) to trigger the code path that performs the boundary-inconsistent check at path (a). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Real-world risk is low to moderate. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local user on an IBM z/VM guest system where hvc_iucv_devices is configured to 8 triggers the driver path where `num == hvc_iucv_devices == 8`, causing `hvc_iucv_table[8]` to be dereferenced. This out-of-bounds kernel memory access results in a kernel panic and system crash. … |
| Remediation | Update to the appropriate patched stable kernel release: 5.10.258, 5.15.209, 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10, or 7.1, per the EUVD-2026-39841 advisory. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-193 – Off-by-one Error
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External POC / Exploit Code
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