CVE-2026-5818

Unauthorized MCU firmware execution via discarded authorization result

Published Jun 23, 2026 · Updated Jun 24, 2026

Authentication bypass in Caliptra Core Runtime Firmware 2.0.0 through 2.0.1 and 2.1.0 allows attackers to execute unauthorized MCU firmware. ActivateFirmwareCmd::activate_fw discards the result of Caliptra's firmware authorization check during a hitless update instead of rejecting a failed check. Exploitation requires high privileges and an adjacent position, and a time-of-check/time-of-use condition lets altered MCU firmware load without detection or reporting.

CVSS severity7.2
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Caliptra Core Runtime Firmware 2.0.0 through 2.0.1 and 2.1.0 allows attackers to execute unauthorized MCU firmware. ActivateFirmwareCmd::activate_fw discards the result of Caliptra's firmware authorization check during a hitless update instead of rejecting a failed check. Exploitation requires high privileges and an adjacent position, and a time-of-check/time-of-use condition lets altered MCU firmware load without detection or reporting.

The record

CVE
CVE-2026-5818
Published
Jun 23, 2026
Updated
Jun 24, 2026
Vendor
Caliptra
Product
Caliptra Runtime Firmware
Classifications
CWE-253, CAPEC-115, T1542.001
Attack vector
adjacent
Privileges
admin

Timeline

How it unfolded

  1. Jun 23, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 24, 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=2.0.0 <=2.0.1
  2. Affected versionversion=2.1.0

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesadmin

What is affected?

Caliptra · Caliptra Runtime Firmwareversion=2.0.0 <=2.0.1; version=2.1.0

Published CVSS scores

7.2CaliptraCVSS:4.0/AV:A/AC:L/AT:P/PR:H/UI:N/VC:N/VI:H/VA:H/SC:H/SI:H/SA: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-253Incorrect Check of Function Return Value
CAPEC-115Authentication Bypass
T1542.001Pre-OS Boot: System Firmware

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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