Auth bypass in IBM I

CVE-2026-18221

IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to gain unauthorized access due to improper validation of client-supplied authentication parameters.

Vulnerability class: Broken Authentication

Published · last modified .

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.003 (25.9th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-18221: held from 0.003 to 0.003.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.000

Affected products

  • IBM I — versions 7.3, 7.4, 7.5

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-18221?
CVE-2026-18221 is a high-severity vulnerability in IBM I, classified under Improper Authentication. CVSS score: 8.1/10. Published 2026-09-04.
How severe is CVE-2026-18221?
High severity. CVSS v3 base score is 8.1 out of 10.