CVE-2026-16661
Authenticated FSP access allows arbitrary code execution in IBM PowerVM firmware.
Is CVE-2026-16661 being exploited?
Not confirmed. CVE-2026-16661 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 0.13% probability of exploitation in the next 30 days.
How severe is CVE-2026-16661?
CVE-2026-16661 is rated High. 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-2026-16661?
Yes. A fix has been recorded for CVE-2026-16661. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-16661 affect?
CVE-2026-16661 affects IBM PowerVM Hypervisor (FSP mailbox interface), FW1120.00, FW1110.00 - FW1110.30, FW1060.00 - FW1060.80, and 1 further product or version. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-16661?
Restrict/segment FSP access, rotate creds, and apply IBM firmware updates when released.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated service-level FSP access enables arbitrary code execution in host firmware, granting full control of the managed system (C/I/A compromise).
Immediate action required
- affectedFW1120.00
- affected>= FW1110.00 and <= FW1110.30
- affected>= FW1060.00 and <= FW1060.80
- affected>= FW950.00 and <= FW950.H2
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.