VulnerabilityPublished 26 Jun 2026Updated 6 Nov 2026

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

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in fed8b8f33a46db0ee2efdb000f4f630c86ed8ca4 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:49 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in fed8b8f33a46db0ee2efdb000f4f630c86ed8ca4, f2a880e802ad12d1e38039d1334fb1475d0f5241, f1dc8e72de9aabe5d96767a4e97219ac26b79fe5 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 26 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 44a01d5ba8a4d543694461cd3e178cfa6b3f221b, < fed8b8f33a46db0ee2efdb000f4f630c86ed8ca4	Fixed in fed8b8f33a46db0ee2efdb000f4f630c86ed8ca4
LinuxLinux	Affected ≥ 44a01d5ba8a4d543694461cd3e178cfa6b3f221b, < f2a880e802ad12d1e38039d1334fb1475d0f5241	Fixed in f2a880e802ad12d1e38039d1334fb1475d0f5241
LinuxLinux	Affected ≥ 44a01d5ba8a4d543694461cd3e178cfa6b3f221b, < f1dc8e72de9aabe5d96767a4e97219ac26b79fe5	Fixed in f1dc8e72de9aabe5d96767a4e97219ac26b79fe5
LinuxLinux	Affected ≥ 44a01d5ba8a4d543694461cd3e178cfa6b3f221b, < a76511bc654819425d3b15e77b523d7f9d81f064	Fixed in a76511bc654819425d3b15e77b523d7f9d81f064
LinuxLinux	Affected ≥ 44a01d5ba8a4d543694461cd3e178cfa6b3f221b, < 484357dff256c816d9466bda35eb765685e4dc86	Fixed in 484357dff256c816d9466bda35eb765685e4dc86
LinuxLinux	Affected ≥ 44a01d5ba8a4d543694461cd3e178cfa6b3f221b, < 11207e42a332eb8bbcb9fe74df9edd2a807c5607	Fixed in 11207e42a332eb8bbcb9fe74df9edd2a807c5607

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.

References

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