CVE-2026-53306

MEDIUMNVD 5.55.5—
EchelonGraph scoreHIGH confidence

Score 5.5 from GitHub Security Advisory published 2026-06-26. NVD baseline CVSS 5.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
5.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.5
EG Score
5.5(high)
EG Risk
—
EPSS
2.5%
KEV
Not listed

Published

June 26, 2026

Last Modified

July 6, 2026

Advisory Details (8)

Auto-updated Jul 8, 2026
No patch confirmed yet.
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/fed8b8f33a46db0ee2efdb000f4f630c86ed8ca4
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f2a880e802ad12d1e38039d1334fb1475d0f5241
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/f1dc8e72de9aabe5d96767a4e97219ac26b79fe5
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/a76511bc654819425d3b15e77b523d7f9d81f064
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/484357dff256c816d9466bda35eb765685e4dc86
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/3d3b89e6ab93bdd0efd45828bda6b0e61cc46dff
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/3104a3f40feb107f77d7116ad9bf6c210ab7babf
generic

tty: hvc_iucv: fix off-by-one in number of supported devices - kernel/git/stable/linux.git - Linux kernel stable tree

https://git.kernel.org/stable/c/11207e42a332eb8bbcb9fe74df9edd2a807c5607

Vendor Advisories for CVE-2026-53306(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 54× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:25 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 14:31 UTCEPSS rescore
  6. 2026-07-19 02:29 UTCEPSS rescore
  7. 2026-07-18 10:04 UTCEPSS rescore
  8. 2026-07-16 17:40 UTCGHSA enrichment
  9. 2026-07-16 17:03 UTCEPSS rescore
  10. 2026-07-15 18:48 UTCGHSA enrichment
  11. 2026-07-15 16:57 UTCEPSS rescore
  12. 2026-07-15 16:57 UTCEPSS rescore
  13. 2026-07-15 02:00 UTCEPSS rescore
  14. 2026-07-15 02:00 UTCEPSS rescore
  15. 2026-07-14 19:56 UTCGHSA enrichment
  16. 2026-07-13 22:31 UTCEPSS rescore
  17. 2026-07-13 21:04 UTCGHSA enrichment
  18. 2026-07-12 22:12 UTCGHSA enrichment
  19. 2026-07-12 05:46 UTCEPSS rescore
  20. 2026-07-11 23:20 UTCGHSA enrichment
  21. 2026-07-11 08:27 UTCEPSS rescore
  22. 2026-07-11 08:27 UTCEPSS rescore
  23. 2026-07-11 00:28 UTCGHSA enrichment
  24. 2026-07-10 01:36 UTCGHSA enrichment
  25. 2026-07-09 19:10 UTCEPSS rescore
Show 29 more
  1. 2026-07-09 19:10 UTCEPSS rescore
  2. 2026-07-09 02:41 UTCGHSA enrichment
  3. 2026-07-08 15:16 UTCEPSS rescore
  4. 2026-07-08 15:16 UTCEPSS rescore
  5. 2026-07-08 03:49 UTCEG score recompute▲ 5.50
  6. 2026-07-08 03:49 UTCGHSA enrichment
  7. 2026-07-07 13:46 UTCEPSS rescore
  8. 2026-07-07 13:46 UTCEPSS rescore
  9. 2026-07-06 21:35 UTCNVD updateCVSS v3 → 5.5 · severity → MEDIUM
  10. 2026-07-06 16:27 UTCEPSS rescore
  11. 2026-07-06 16:27 UTCEPSS rescore
  12. 2026-07-06 02:23 UTCEPSS rescore
  13. 2026-07-06 02:23 UTCEPSS rescore
  14. 2026-07-05 08:17 UTCGHSA enrichment
  15. 2026-07-05 02:31 UTCEPSS rescore
  16. 2026-07-05 02:30 UTCEPSS rescore
  17. 2026-07-04 06:31 UTCEPSS rescore
  18. 2026-07-04 06:31 UTCEPSS rescore
  19. 2026-07-02 12:44 UTCGHSA enrichment
  20. 2026-07-01 15:07 UTCEPSS rescore
  21. 2026-06-30 23:22 UTCEPSS rescore
  22. 2026-06-29 17:10 UTCGHSA enrichment
  23. 2026-06-29 14:06 UTCEPSS rescore
  24. 2026-06-29 14:06 UTCEPSS rescore
  25. 2026-06-28 14:07 UTCEPSS rescore
  26. 2026-06-28 04:56 UTCEPSS rescore
  27. 2026-06-28 04:56 UTCEPSS rescore
  28. 2026-06-26 21:37 UTCEG score recompute
  29. 2026-06-26 21:37 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2026-53306?
CVE-2026-53306 is a medium vulnerability published on June 26, 2026. In the Linux kernel, the following vulnerability has been resolved: tty: hvc_iucv: fix off-by-one in number of supported devices MAXHVCIUCVLINES == HVCALLOCTTYADAPTERS == 8. This is the number of entries in: static struct hvciucvprivate *hvciucvtable[MAXHVCIUCV_LINES]; Sometimes hvciucvtable[] is…
When was CVE-2026-53306 disclosed?
CVE-2026-53306 was first published in the National Vulnerability Database on June 26, 2026, with the most recent update on July 6, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53306 actively exploited?
CVE-2026-53306 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 2.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-53306?
CVE-2026-53306 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-53306?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-53306, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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