How severe is CVE-2021-27657?

CVE-2021-27657 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-27657 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27657?

CVE-2021-27657 affects Johnsoncontrols Metasys. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27657?

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.

When was CVE-2021-27657 published?

CVE-2021-27657 was published on 2021-06-04 and last updated on 2026-06-17.

CVE-2021-27657

CVE-2021-27657 is a high-severity vulnerability in Johnsoncontrols Metasys with a CVSS 3.x base score of 8.8. 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-269.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.5
EPSS exploit prediction: 1% (66th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-269
Affected product: Johnsoncontrols Metasys
Published: 2021-06-04
Last modified: 2026-06-17

Description

Successful exploitation of this vulnerability could give an authenticated Metasys user an unintended level of access to the server file system, allowing them to access or modify system files by sending specifically crafted web messages to the Metasys system. This issue affects: Johnson Controls Metasys version 11.0 and prior versions.

Frequently asked questions

What is CVE-2021-27657?: Successful exploitation of this vulnerability could give an authenticated Metasys user an unintended level of access to the server file system, allowing them to access or modify system files by sending specifically crafted web messages to the Metasys system. This issue affects: Johnson Controls Metasys version 11.0 and prior versions.
How severe is CVE-2021-27657?: CVE-2021-27657 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-27657 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (66th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27657?: CVE-2021-27657 affects Johnsoncontrols Metasys. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27657?: 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.
When was CVE-2021-27657 published?: CVE-2021-27657 was published on 2021-06-04 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:johnsoncontrols:metasys:*:*:*:*:*:*:*:*

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