What is CVE-2021-27657?

CVE-2021-27657 is a high-severity vulnerability in Johnson Controls Metasys, classified under Improper Privilege Management. CVSS score: 8.8/10. Published 2021-06-04.

How severe is CVE-2021-27657?

High severity. CVSS v3 base score is 8.8 out of 10.

Privilege escalation in Johnson Controls Metasys

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.

Vulnerability class: Privilege Escalation

Published 2021-06-04 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.012 (68.1th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 68th percentile — 68.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.012 · change: 0.000

Affected products

Johnson Controls Metasys — versions 11.0
Johnsoncontrols Metasys

Weakness classification (CWE)

CWE-269 — Improper Privilege Management

References

www.johnsoncontrols.com/cyber-solutions/security-advisories (Vendor Advisory)
us-cert.gov/ics/advisories (US Government Resource, Third Party Advisory, third-party-advisory)
us-cert.cisa.gov/ics/advisories/icsa-21-159-01 (US Government Resource, Third Party Advisory, third-party-advisory)

Frequently asked questions

What is CVE-2021-27657?: CVE-2021-27657 is a high-severity vulnerability in Johnson Controls Metasys, classified under Improper Privilege Management. CVSS score: 8.8/10. Published 2021-06-04.
How severe is CVE-2021-27657?: High severity. CVSS v3 base score is 8.8 out of 10.