CVE-2026-16661

Firmware code execution via mailbox integer overflow

Published Aug 19, 2026 · Updated Aug 19, 2026

Integer overflow in affected IBM PowerVM Hypervisor firmware allows attackers to execute arbitrary code in the host firmware runtime. The service processor mailbox interface performs an integer calculation that can overflow while processing FSP requests; IBM has not disclosed the affected routine or arithmetic operation. Authenticated service-level FSP access is required, and successful exploitation grants full control of the managed system.

CVSS severity8.2
High
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in affected IBM PowerVM Hypervisor firmware allows attackers to execute arbitrary code in the host firmware runtime. The service processor mailbox interface performs an integer calculation that can overflow while processing FSP requests; IBM has not disclosed the affected routine or arithmetic operation. Authenticated service-level FSP access is required, and successful exploitation grants full control of the managed system.

The record

CVE
CVE-2026-16661
Published
Aug 19, 2026
Updated
Aug 19, 2026
Vendor
IBM
Product
PowerVM Hypervisor
Classifications
CWE-190, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Aug 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=FW1060.00 <=FW1060.80
  2. Affected versionversion=FW1110.00 <=FW1110.30
  3. Affected versionversion=FW1120.00
  4. Affected versionversion=FW950.00 <=FW950.H2

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

IBM · PowerVM Hypervisorversion=FW1060.00 <=FW1060.80; version=FW1110.00 <=FW1110.30; version=FW1120.00; version=FW950.00 <=FW950.H2

Published CVSS scores

8.2IBMCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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