Affects widely used IBM WebSphere application servers; allows remote arbitrary class instantiation via IIOP which can lead to JVM code execution and enterprise impact.
CVE-2026-8400
IIOP flaw in WebSphere allows remote arbitrary Java class loading/instantiation
Is CVE-2026-8400 being exploited?
Not confirmed. CVE-2026-8400 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.27% probability of exploitation in the next 30 days.
How severe is CVE-2026-8400?
CVE-2026-8400 is rated High with a CVSS score of 8.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-8400?
Yes. A fix has been recorded for CVE-2026-8400. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-8400 affect?
CVE-2026-8400 affects IBM WebSphere Application Server 8.5, IBM WebSphere Application Server 9.0, IBM WebSphere Liberty Continuous Delivery, IBM SDK, Java Technology Edition (ORB component). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-8400?
Apply vendor patch when available; block/limit IIOP; disable untrusted IIOP endpoints
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Malicious IIOP server can force loading/instantiation of arbitrary Java classes, enabling remote code execution or unauthorized code execution in the JVM.
Immediate action required
- affected8.5
- affected9.0
- affectedContinuous delivery
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.