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China-Linked Fire Ant Hijacks Cisco Routers to Steal Credentials and Blind Security Logs
China-nexus espionage group Fire Ant compromised Cisco IOS XR routers and TACACS servers to harvest credentials, capture traffic and suppress logs.
Sygnia investigated an intrusion in which Fire Ant expanded beyond VMware hypervisors to Cisco IOS XR routers, TACACS servers and Linux management hosts. The actor deployed purpose-built router implants that hid a GRE tunnel, filtered log messages, captured PCAPs uploaded to external FTP servers, and used TacTap to inject a library into tac_plus and steal TACACS credentials obfuscated with a single-byte XOR key of 0xEF. A Linux backdoor named BridgeAgent masqueraded as a Zabbix agent, persisted via a root systemd unit, disguised itself as /usr/bin/gnome-shell and received commands over TLS on port 443. The group also used Medusa and REPTILE rootkits, SSH backdoors and renamed binaries impersonating SentinelOne and Cybereason agents, while suppressing logs, disabling SELinux and rewriting login history. Sygnia assesses strong overlap with UNC3886 and published IoCs.
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China's 'Fire Ant' campaign used compromised Cisco routers as platform for more attacks
Sygnia links the China-nexus Fire Ant campaign to UNC3886, showing hackers weaponized compromised Cisco IOS XR routers for espionage and wider intrusions.
Sygnia's Fire Ant report details Chinese hackers compromising Cisco IOS XR routers, TACACS+ authentication servers and management infrastructure to capture traffic, harvest credentials and stage attacks on high-value and critical infrastructure networks. The group, which overlaps with Mandiant's UNC3886, developed custom router malware for persistence, hid logs, deleted files and tampered with firewall rules, and remained active in 2026 after Sygnia's 2025 disclosure. The activity aligns with prior Chinese campaigns against Cisco devices, including Volt Typhoon and Salt Typhoon operations.
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Cisco bundles fixes for multiple vulnerabilities, some critical, into one patch
Cisco patched seven IOS XR vulnerabilities, two rated CVSS 9.8, allowing unauthenticated remote code execution and root access on carrier routers; no exploitation observed.
Cisco released fixes for seven internally discovered vulnerabilities in IOS XR, its Linux-based network operating system for carrier-grade routers. Two flaws, CVE-2026-20274 and CVE-2026-20279, are rated CVSS 9.8 (critical) and involve lifetime resource control issues that can enable unauthenticated remote code execution with root access; the other five are rated 8.2-8.8 and cover buffer overflows, access control failures, and out-of-bounds access. All IOS XR releases including IOS XR7 are affected regardless of configuration, no workarounds exist, and remediation requires software maintenance upgrades (SMUs) or fixed releases 26.2.2/26.3.1. Cisco says the flaws are not known to be actively exploited, but experts urge immediate patching of internet-facing and core routing systems, citing parallels with Salt Typhoon tradecraft.
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