CVE-2021-20593
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIncorrect Implementation of Authentication Algorithm in Mitsubishi Electric Air Conditioning System/Centralized Controllers (G-50A Ver.2.50 to Ver. 3.35, GB-50A Ver.2.50 to Ver. 3.35, AG-150A-A Ver.3.20 and prior, AG-150A-J Ver.3.20 and prior, GB-50ADA-A Ver.3.20 and prior, GB-50ADA-J Ver.3.20 and prior, EB-50GU-A Ver 7.09 and prior, EB-50GU-J Ver 7.09 and prior, AE-200A Ver 7.93 and prior, AE-200E Ver 7.93 and prior, AE-50A Ver 7.93 and prior, AE-50E Ver 7.93 and prior, EW-50A Ver 7.93 and prior, EW-50E Ver 7.93 and prior, TE-200A Ver 7.93 and prior, TE-50A Ver 7.93 and prior, TW-50A Ver 7.93 and prior, CMS-RMD-J Ver.1.30 and prior) and Air Conditioning System/Expansion Controllers (PAC-YG50ECA Ver.2.20 and prior) allows a remote authenticated attacker to impersonate administrators to disclose configuration information of the air conditioning system and tamper information (e.g. operation information and configuration of air conditioning system) by exploiting this vulnerability.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceIncorrect implementation of the authentication algorithm in Mitsubishi Electric HVAC controllers allows a remote authenticated attacker to bypass proper authorization and impersonate administrators. This enables disclosure of system configuration and tampering with operational settings.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 2.50, <= 3.35>= 2.50, <= 3.35<= 3.20<= 3.20<= 3.20<= 3.20<= 7.09<= 7.09CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify HVAC controller model and firmware versionAccess the device's web management interface or check the device label/display for the model number (G 50a, Gb 50a, AG 150a, Gb 50ada, or Eb 50gu) and navigate to the firmware version information page typically found under System Information, Maintenance, or About sectionsAffected if The model matches one of the affected products (G 50a, Gb 50a, AG 150a A/J, Gb 50ada A/J, or Eb 50gu A/J) AND the firmware version falls within the affected ranges (2.50-3.35 for G 50a/Gb 50a, <=3.20 for AG 150a/Gb 50ada, or <=7.09 for Eb 50gu)
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Verify if remote management interface is exposedCheck your network configuration to determine if the HVAC controller's web interface or management ports (typically HTTP/HTTPS on ports 80/443 or vendor-specific ports) are accessible from external networks or the internetAffected if The management interface is accessible from untrusted networks without proper network segmentation or firewall restrictions
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Review administrator account activity logsExamine the device's built-in logging or audit logs for the HVAC controller, looking for administrative actions, configuration changes, or login events that originate from unexpected IP addresses or occur at unusual times, particularly actions related to user privilege changes or system configuration exportsAffected if Logs show administrative actions performed by accounts that should not have had those privileges, or duplicate admin sessions occurring simultaneously
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Inspect user account configuration for anomaliesReview the user management section of the HVAC controller to identify any unauthorized changes to administrative accounts, unexpected new admin accounts, or privilege escalations that were not initiated by legitimate administratorsAffected if Unexpected administrative accounts exist or legitimate accounts show unauthorized privilege modifications
Your environment is affected if you operate any of the listed Mitsubishi HVAC controller models within the specified firmware version ranges and the device management interface is network-accessible to potential attackers.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataApply vendor-supplied firmware updates for all affected models; until patches are available, implement network segmentation to restrict access to HVAC controllers and monitor for unauthorized administrative actions.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20593 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-20593 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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