Sierra Wireless AirLink ALEOS: file access flaw under attack

What is affected

Sierra Wireless AirLink ALEOS is mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have it yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

Sierra Wireless AirLink ALEOS contains an unrestricted upload of file with dangerous type vulnerability. A specially crafted HTTP request can upload a file, resulting in executable code being uploaded, and routable, to the webserver. An attacker can make an authenticated HTTP request to trigger this vulnerability. The impacted product could be end-of-life (EoL) and/or end-of-service (EoS). Users should discontinue product utilization.

What an attacker can do

This is a file access flaw. It lets an attacker read or write files they should never reach, such as configuration files that hold passwords, or upload a malicious file that the system then runs.

How it is reached

Over the internet or network

Access the attacker needs

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer Sierra Wireless AirLink ALEOS at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• source.sierrawireless.comsource.sierrawireless.com/resources/airlink/software_reference_docs/technical-bulletin/sie
• source.sierrawireless.comsource.sierrawireless.com/resources/airlink/hardware_reference_docs/airlink_es450_eol

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on December 12, 2025, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by January 2, 2026, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 27% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 98% of all scored vulnerabilities.

Its CVSS severity score is 8.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

An exploitable remote code execution vulnerability exists in the upload.cgi functionality of Sierra Wireless AirLink ES450 FW 4.9.3. A specially crafted HTTP request can upload a file, resulting in executable code being uploaded, and routable, to the webserver. An attacker can make an authenticated HTTP request to trigger this vulnerability.