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Linux Kernel CVE-2026-53306

| EUVDEUVD-2026-39841 MEDIUM
Off-by-one Error (CWE-193)
2026-06-26 Linux GHSA-v222-hvcr-rghc
Information Disclosure Linux Red Hat Suse
5.5
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
5.5 MEDIUM

Local-only kernel driver path (AV:L), low-privilege trigger (PR:L), no confidentiality or integrity impact, kernel panic yields high availability loss.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
6.1 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:H
Red Hat
5.5 MEDIUM
qualitative

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

5
Analysis Generated
Jul 06, 2026 - 20:30 vuln.today
CVSS changed
Jul 06, 2026 - 20:22 NVD
5.5 (MEDIUM)
Patch available
Jun 26, 2026 - 21:02 EUVD
CVE Published
Jun 26, 2026 - 19:41 cve.org
UNKNOWN (no severity yet)
CVE Published
Jun 26, 2026 - 19:41 nvd
MEDIUM 5.5

DescriptionNVD

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. No public exploit identified at time of analysis; EPSS is 0.18% (7th percentile), consistent with a niche mainframe-only driver affecting a very limited deployment population.

Technical ContextAI

The hvc_iucv driver (drivers/tty/hvc/hvc_iucv.c) provides HVC (Hypervisor Virtual Console) terminal access over IUCV (Inter-User Communication Vehicle) on IBM z/VM mainframe hypervisors. The static array hvc_iucv_table[MAX_HVC_IUCV_LINES] holds 8 entries (valid indices 0-7). CWE-193 (Off-by-One Error) manifests because the boundary check at path (a) uses a strict greater-than comparison - if (num > hvc_iucv_devices) - which permits num hvc_iucv_devices 8, allowing access to hvc_iucv_table[8], one element beyond the array's end. The iterator at path (b) uses i < hvc_iucv_devices, which is correct and stays within bounds, but path (a) is inconsistent. CPE cpe:2.3:a:linux:linux:*:*:*:*:*:*:*:* applies from the initial introduction (commit 44a01d5ba8a4d, Linux 2.6.29) through the patched stable releases.

RemediationAI

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. Patch commits are available at https://git.kernel.org/stable/c/3d3b89e6ab93bdd0efd45828bda6b0e61cc46dff and sibling stable-tree commits referenced in the CVE. As a compensating control where patching is not immediately feasible, restrict the hvc_iucv_devices kernel module parameter to a value of 7 or fewer (e.g., append hvc_iucv=7 to the kernel command line) to prevent the boundary condition from being reached; this reduces the number of available HVC IUCV consoles but eliminates the out-of-bounds access. Alternatively, unload or blacklist the hvc_iucv module if IUCV-based HVC consoles are not required - note this removes all IUCV terminal access for z/VM guests relying on this driver.

Same weakness CWE-193 – Off-by-one Error

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
Container suse/sl-micro/6.0/base-os-container:2.1.3-7.177 Container suse/sl-micro/6.1/base-os-container:2.2.1-5.155 Affected
Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.206 Container suse/sl-micro/6.1/rt-os-container:2.2.1-5.152 Affected
Image SLES15-SP7-Azure-3P Image SLES15-SP7-Azure-Basic Image SLES15-SP7-Azure-Standard Image SLES15-SP7-HPC-Azure Affected
Image SLES15-SP7-BYOS-Azure Image SLES15-SP7-BYOS-GCE Image SLES15-SP7-CHOST-BYOS-Aliyun Image SLES15-SP7-CHOST-BYOS-Azure Image SLES15-SP7-CHOST-BYOS-EC2 Image SLES15-SP7-CHOST-BYOS-GCE Image SLES15-SP7-CHOST-BYOS-GDC Image SLES15-SP7-CHOST-BYOS-SAP-CCloud Image SLES15-SP7-EC2 Image SLES15-SP7-EC2-ECS-HVM Image SLES15-SP7-GCE Image SLES15-SP7-HPC-BYOS-Azure Image SLES15-SP7-HPC-BYOS-EC2 Image SLES15-SP7-HPC-BYOS-GCE Image SLES15-SP7-Hardened-BYOS-Azure Image SLES15-SP7-Hardened-BYOS-EC2 Image SLES15-SP7-Hardened-BYOS-GCE Image SLES15-SP7-SAPCAL-Azure Image SLES15-SP7-SAPCAL-EC2 Image SLES15-SP7-SAPCAL-GCE Affected
Image SLES15-SP7-SAP-Azure Image SLES15-SP7-SAP-Azure-3P Image SLES15-SP7-SAP-BYOS-Azure Image SLES15-SP7-SAP-BYOS-EC2 Image SLES15-SP7-SAP-BYOS-GCE Image SLES15-SP7-SAP-EC2 Image SLES15-SP7-SAP-GCE Image SLES15-SP7-SAP-Hardened-Azure Image SLES15-SP7-SAP-Hardened-BYOS-Azure Image SLES15-SP7-SAP-Hardened-BYOS-EC2 Image SLES15-SP7-SAP-Hardened-BYOS-GCE Image SLES15-SP7-SAP-Hardened-GCE Affected

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CVE-2026-53306 vulnerability details – vuln.today
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