Cybersecurity · · 1 min read

Understanding the Sierra:21 Vulnerabilities in Sierra Wireless Routers

Understanding the Sierra:21 Vulnerabilities in Sierra Wireless Routers

A recent discovery has highlighted a significant concern within the Sierra Wireless AirLink cellular routers. Dubbed "Sierra:21" this collection of security flaws presents a substantial risk to critical sectors.

Unpacking Sierra:21

Sierra:21 is a series of 21 security vulnerabilities found in Sierra Wireless AirLink routers and associated open-source software components​​. These flaws vary in severity, with one classified as critical, nine as high, and the remaining 11 as medium​​.

Potential Impact

The vulnerabilities have far-reaching implications, given that they impact over 86,000 devices across vital sectors like energy, healthcare, and emergency services predominantly in the U.S., Canada, Australia, France, and Thailand​​. The nature of these flaws could allow attackers to:

  • Steal credentials
  • Inject malicious code to take control of routers
  • Use compromised devices as entry points into critical networks​​

Additionally, the vulnerabilities include risks like remote code execution (RCE), cross-site scripting (XSS), denial-of-service (DoS), unauthorized access, and authentication bypasses. Such weaknesses can be exploited for credential theft, crashing management applications, and conducting adversary-in-the-middle (AitM) attacks​​.

Enhanced Threat Landscape

A particularly alarming aspect of Sierra:21 is the potential for these vulnerabilities to be exploited by botnet malware. This could lead to:

  • Worm-like automatic propagation
  • Communication with command-and-control (C2) servers
  • Enslaving affected machines to launch distributed denial-of-service (DDoS) attacks​​

Mitigation Efforts

Fortunately, fixes have been released for these flaws in specific versions of ALEOS and OpenNDS. However, for components like TinyXML, which are no longer actively maintained, mitigation needs to be addressed by affected vendors​​.


The discovery of Sierra:21 highlights the vulnerability of essential infrastructure to cyber attacks. This situation underscores the critical necessity for stringent cybersecurity protocols, especially within systems crucial to our society's operations. Actively detecting and addressing these security gaps is imperative to prevent potential malicious activities, which could result in significant network interruptions, covert surveillance, and the widespread distribution of harmful malware.

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