A Russian-linked cyber group known as Static Tundra has been actively exploiting a seven-year-old flaw in Cisco IOS and IOS XE software, targeting organizations worldwide, Cisco Talos reported Wednesday.
The vulnerability, identified as CVE-2018-0171 with a CVSS score of 9.8, exists in Cisco’s Smart Install feature. It allows remote, unauthenticated attackers to trigger denial-of-service conditions or execute arbitrary code. Despite patches being available since 2018, unpatched and end-of-life devices remain a prime target for exploitation.
Static Tundra Persistent Threat Targeting Key Sectors
Cisco Talos researchers confirmed that the attacks focus on industries such as telecommunications, higher education, and manufacturing across North America, Asia, Africa, and Europe. Static Tundra’s approach relies on maintaining long-term persistence within victim networks to gather intelligence, highlighting the risks organizations face when outdated systems remain connected to operational environments.
Over the past year, threat actors have exploited the flaw to collect configuration files from thousands of networking devices, particularly in U.S. critical infrastructure sectors. Attackers have also been observed modifying device configurations to enable unauthorized access, laying the foundation for deeper reconnaissance inside compromised networks.
Techniques and Tools for Long-Term Access
According to Cisco Talos, Static Tundra leverages a combination of network scanning tools and custom malware to expand its footprint. Publicly available scanning services such as Shodan and Censys are believed to help identify vulnerable systems. Once access is established, the attackers often deploy SYNful Knock, a stealthy firmware modification first documented in 2015. This implant enables persistence, is modular in design, and can be updated after installation to match evolving operational objectives.
Attackers also exploit the Simple Network Management Protocol (SNMP) to issue instructions for downloading malicious text files from remote servers, which are then appended to live configurations. This provides additional avenues for control while evading detection by altering authentication and logging mechanisms. By modifying TACACS+ configurations, adversaries interfere with monitoring tools, allowing them to remain hidden while maintaining unauthorized access.
A notable tactic includes the use of Generic Routing Encapsulation (GRE) tunnels to reroute network traffic of interest to attacker-controlled infrastructure. In parallel, adversaries exfiltrate NetFlow data from compromised systems, transmitting it via outbound TFTP or FTP connections. These techniques allow the group to capture high-value network traffic while maintaining operational stealth.
Mitigation and Security Recommendations
Cisco has issued updated guidance regarding CVE-2018-0171, emphasizing the importance of applying the available patches or disabling Smart Install if upgrading is not immediately possible. The company warns that exploitation attempts remain ongoing, particularly against devices that are no longer supported by regular updates.
Organizations are urged to:
- Apply available patches immediately for Cisco IOS and IOS XE software.
- Disable Smart Install on devices where it is not required.
- Audit and monitor device configurations to detect unauthorized changes.
- Implement continuous monitoring to identify unusual traffic patterns or the creation of GRE tunnels.
- Replace end-of-life hardware that cannot be patched or secured against vulnerabilities.
The continued exploitation of this vulnerability demonstrates the importance of timely patch management and proactive defense. Even years after disclosure, unpatched flaws in widely deployed devices remain a serious security concern, especially when targeted by advanced adversaries.
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