How severe is CVE-2026-5818?

CVE-2026-5818 has a CVSS 4.0 base score of 7.2, rated high severity.

Is CVE-2026-5818 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-5818?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-5818 have an EU (EUVD) identifier?

Yes. CVE-2026-5818 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38638.

When was CVE-2026-5818 published?

CVE-2026-5818 was published on 2026-06-24 and last updated on 2026-06-25.

CVE-2026-5818

CVE-2026-5818 is a high-severity vulnerability with a CVSS 4.0 base score of 7.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-253.

Key facts

Severity: High (CVSS 4.0 base score 7.2)
EPSS exploit prediction: 0% (5th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38638
Weakness: CWE-253
Published: 2026-06-24
Last modified: 2026-06-25

Description

Incorrect check of function return value in Caliptra Core Runtime Firmware (ActivateFirmwareCmd::activate_fw modules) allows bypass of Caliptra Core's verification of the MCU FW during a hitless update. This issue affects Core Runtime Firmware: from 2.0.0 through 2.0.1, 2.1.0.

Frequently asked questions

What is CVE-2026-5818?: Incorrect check of function return value in Caliptra Core Runtime Firmware (ActivateFirmwareCmd::activate_fw modules) allows bypass of Caliptra Core's verification of the MCU FW during a hitless update. This issue affects Core Runtime Firmware: from 2.0.0 through 2.0.1, 2.1.0.
How severe is CVE-2026-5818?: CVE-2026-5818 has a CVSS 4.0 base score of 7.2, rated high severity.
Is CVE-2026-5818 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (5th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-5818?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-5818 have an EU (EUVD) identifier?: Yes. CVE-2026-5818 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38638.
When was CVE-2026-5818 published?: CVE-2026-5818 was published on 2026-06-24 and last updated on 2026-06-25.

References

https://github.com/chipsalliance/caliptra-sw/security/advisories/GHSA-456r-gcjr-6rxq

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