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CVE-2026-53306: tty: hvc_iucv: fix off-by-one in number of supported devices

highCVSS 7.1CVE-2026-53306

CSIRTS triage

Privilege escalation
What
The vulnerability is an off-by-one error in the number of supported devices in the tty: hvc_iucv subsystem.
Who is affected
Deployments using the tty: hvc_iucv subsystem may be affected.
Urgency
Remediation is high urgency due to the high severity rating.
Action
Apply the relevant patches as soon as possible.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
high — CVSS 7.1
Published
2026-06-09
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-53306

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-53306coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

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