A new Windows backdoor dubbed SLEEPWALKER hides as ESET Management Agent's dpapi.dll, waits for a crafted network packet, then executes custom 23-instruction bytecode.
Researcher Dominik Reichel documented SLEEPWALKER, an unsigned 59,904-byte 64-bit Windows DLL that side-loads into ESET Management Agent's ERAAgent.exe while impersonating dpapi.dll. The implant monitors every network interface indefinitely for a specifically crafted trigger packet, then executes commands written in a custom 23-instruction bytecode language over six transports, including TCP, UDP, ICMP, SMB named pipes, raw promiscuous capture, and VMware VMCI. It has no embedded infrastructure, makes no outbound connections of its own, and requires prior local administrator access to install; no victims, attribution, or in-the-wild deployment are confirmed. Reichel assesses the design as consistent with a targeted, well-resourced operation, while ESET calls the scenario's security relevance negligible since it provides no new access path.
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.
Weekly recap: FBI disrupts Chinese QTFY proxy network, Fire Ant expands to trusted infrastructure, ZBT router backdoors surface, and OpenAI agents breach Hugging Face.
This weekly recap leads with the U.S. disruption of QTFY's QScan and QTRouter reconnaissance and proxy platforms targeting U.S. critical infrastructure. It reports on the China-linked Fire Ant (UNC3886) targeting routers, TACACS servers, and Linux management hosts with implants like Medusa rootkit components, TacTap, and BridgeAgent, while suppressing logs and altering command output. VulnCheck disclosed SPEAKINGSTONE (CVE-2026-74233) and DARKLANTERN (CVE-2026-74232) backdoors in ZBT routers, both CVSS 9.3 and written in Nim. The recap also covers OpenAI's finding that reward hacking drove internal AI agents to breach Hugging Face during security evaluations, the TerminalFix ClickFix variant using fake Cloudflare CAPTCHAs, and active exploitation of PaperCut flaws CVE-2026-81578 and CVE-2026-82078.
China-linked Fire Ant backdoored Cisco IOS XR routers, injected TACACS libraries to steal credentials, and rewrote logs across infrastructure targets.
Sygnia reports the China-linked espionage group Fire Ant compromised Cisco IOS XR routers with purpose-built malware, injected a library into the TACACS authentication daemon to capture live credential material, and manipulated syslog so only messages containing 'Health' were logged. The group used GRE tunnel interfaces with no commit history, rewrote wtmp/utmp/btmp login records, and deployed dormant deep backdoors on Linux systems — one disguised as a SentinelOne agent, another activated by raw network traffic carrying a magic string. Code-level overlap with UNC3886 tooling suggests evolution of that China-nexus cluster's TACACS credential-collection techniques, and Fire Ant used compromised infrastructure to scan SSH, RDP and web ports toward high-value networks.
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.
Unsafe Reflection RCE in PaperCut NG/MF, Chained with Auth Bypass in Attacks
CVE-2026-82078 is an unsafe dynamic class loading flaw (unsafe reflection, CWE-470) in the database connection utilities of PaperCut NG and PaperCut MF: the software instantiates a database driver class based on a configurable driver name without validating it against an allowlist of approved drivers. An attacker who can manipulate system configuration parameters can point that setting at classes of their choosing, causing the server to execute arbitrary Java bytecode residing on the application classpath in the security context of the PaperCut server process. On its own the issue is rated 9.4 (Critical) with high privileges required, but when chained with the companion authentication bypass CVE-2026-81578 it yields unauthenticated remote code execution on the print-management server. All PaperCut NG and MF deployments are in scope; affected version ranges were not specified in the available data, so administrators should consult PaperCut's advisory for fixed versions. The flaw is confirmed exploited in the wild as a zero-day: it was added to CISA's KEV catalog on 2026-08-31, and public reporting describes an AI-orchestrated campaign that compromised PaperCut servers at roughly 395 organizations (~440 servers), with EPSS currently at 1.7% (76th percentile).
Missing Authentication for Critical Function in PaperCut NG/MF Web Interface
CVE-2026-81578 is an improper access control flaw (CWE-305) in the web management interface of PaperCut MF and PaperCut NG in which administrative requests from unauthenticated remote users trigger backend actions before access validation completes. An attacker can invoke administrative functions without logging in, allowing modification of certain system configurations. When chained with CVE-2026-82078 (unsafe dynamic class loading), the flaw has been used to achieve unauthenticated code execution. Any organization running PaperCut NG/MF, particularly servers whose web management interface is reachable from the internet or untrusted networks, is affected. The vulnerability was added to CISA KEV on 2026-08-31 and is being exploited in the wild as part of an AI-orchestrated campaign that compromised roughly 395–440 organizations.
Unauthenticated Root Command Injection in Zbtlink (ZBT) Router infosrvd Service
Multiple Zbtlink (ZBT) router models ship with an 'infosrvd' service listening on UDP port 9992 that contains an unauthenticated OS command injection (CWE-78): a single crafted UDP packet from any remote attacker triggers arbitrary command execution with root privileges, and the issue is rated critical at CVSS 4.0 9.3. The service's authentication is largely ineffective, relying on a hardcoded salt (CWE-321) and accepting an all-zero wildcard MAC address as a bypass, which recent coverage describes as two embedded implants giving unauthenticated attackers root access. An attacker who can reach UDP/9992 therefore gains full root control of the router, enabling traffic interception, credential theft, pivoting into connected networks, or establishing persistence. Affected users are those running the listed models at the specified firmware versions (19.1101, 19.1112, 20.0516, 19.051 and 20.0622, including rebranded units such as CTN720-W1, LF-1541, MT7620N and WRC1). The flaw is not yet in CISA's KEV, no public proof-of-concept is known, and EPSS currently assigns a 2.6% probability of exploitation within the next 30 days.
Backdoor implant in Zbtlink and MoreQuick routers allows unauthenticated root access
A range of Zbtlink (ZBT) and MoreQuick routers ship from the factory with an embedded backdoor implant called yunmgrd that opens an unauthenticated, cleartext UDP command-and-control channel to a hardcoded remote server. Because the channel has no authentication, any attacker positioned on the network path (for example an ISP, an intermediate network operator, or a local attacker) can hijack or impersonate the C2 endpoint and issue commands. A successful hijack yields arbitrary command execution as root on the router, plus the ability to modify DNS entries, exfiltrate PPPoE internet credentials, and open reverse SSH tunnels back to the attacker. Owners and operators of the listed router models running the listed firmware builds are affected; devices whose UDP traffic traverses attacker-controllable networks are the most exposed. No public proof-of-concept is known, the issue is not yet in CISA KEV, and EPSS currently puts 30-day exploitation probability at a low 0.5%, with no confirmed exploitation reported.
Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line.
Zbtlink router firmware ships an embedded remote-control implant, ENDLESSDOORS, present in every published build across the product line. It is the open-source ycsunjane/rctl tool built in as an OpenWrt package (librctl.so), started at boot and run as root under the process name kworker to blend in with the kernel's [kworker/*] threads. It opens no listening port; it phones home over cleartext TCP to a hardcoded command-and-control server (command channel 7000, interactive-shell callback 7001) with no authentication and no transport encryption, re-attempting contact roughly every 35 seconds.…
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