CVE-2021-40521 is a critical-severity flaw (CVSS 9.8) affecting hsmx-app-25 firmware, hsmx-app-100 firmware, hsmx-app-1000 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Airangel HSMX Gateway devices through 5.2.04 allow Remote Code Execution.
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
Published CVE record published
Updated Record last modified
airangel hsmx-app-25 firmware UPGRADE
Affected: <= 5.2.04
Fixed in: newer than 5.2.04
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
airangel hsmx-app-100 firmware UPGRADE
Affected: <= 5.2.04
Fixed in: newer than 5.2.04
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
airangel hsmx-app-1000 firmware UPGRADE
Affected: <= 5.2.04
Fixed in: newer than 5.2.04
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
airangel hsmx-app-5000 firmware UPGRADE
Affected: <= 5.2.04
Fixed in: newer than 5.2.04
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
airangel hsmx-app-20000 firmware UPGRADE
Affected: <= 5.2.04
Fixed in: newer than 5.2.04
Safe to downgrade to: no unaffected older release
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official sourceNVD · CVE Program · Report a problem with this page Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-40521?
hsmx-app-25 firmware: upgrade to newer than 5.2.04; hsmx-app-100 firmware: upgrade to newer than 5.2.04; hsmx-app-1000 firmware: upgrade to newer than 5.2.04. Exact commands for each OS are on this page.
Is CVE-2021-40521 being exploited?
CVE-2021-40521 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
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