How severe is CVE-2026-53306?

CVE-2026-53306 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-53306 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-53306?

CVE-2026-53306 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-53306?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-53306 published?

CVE-2026-53306 was published on 2026-06-26 and last updated on 2026-07-06.

CVE-2026-53306

CVE-2026-53306 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-193.

Key facts

Severity: Medium (CVSS 3.x base score 5.5)
EPSS exploit prediction: 0% (2nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-193
Affected product: Linux Linux Kernel
Published: 2026-06-26
Last modified: 2026-07-06

Description

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.

Frequently asked questions

What is CVE-2026-53306?: 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.
How severe is CVE-2026-53306?: CVE-2026-53306 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-53306 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-53306?: CVE-2026-53306 affects Linux Linux Kernel. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-53306?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-53306 published?: CVE-2026-53306 was published on 2026-06-26 and last updated on 2026-07-06.

References

Affected products (1)

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

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