Coverage › CVE-2023-39780

CVE-2023-39780 Mapped Sigma

ASUS RT-AX55 Routers OS Command Injection Vulnerability

Vendor / product

ASUS — RT-AX55 Routers

Description (CISA)

ASUS RT-AX55 devices contain an OS command injection vulnerability that could allow a remote, authenticated attacker to execute arbitrary commands. As represented by CVE-2023-41346.

Added to KEV

2025-06-02

Due date

2025-06-23

Required action

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

Known ransomware use

Unknown

CWE

CWE-78

CISA notes

https://www.asus.com/networking-iot-servers/wifi-6/all-series/rt-ax55/helpdesk_bios/?model2Name=RT-AX55
https://www.asus.com/content/asus-product-security-advisory/
https://nvd.nist.gov/vuln/detail/CVE-2023-39780

Elsewhere

cve.org · NVD · CISA KEV · JSON

ATT&CK techniques · CTID Mappings Explorer, ATT&CK 16.1, KEV snapshot 2025-07-28

5 mapping objects across 5 techniques. exploitation technique states how the vulnerability is exploited; primary and secondary impact state what exploitation achieves. They are different claims and are labelled as such.

Detection chain · ATT&CK Enterprise v19.2 detection strategies, analytics, log sources

T1021.004 SSH secondary impact

• DET0596 Behavioral Detection of Remote SSH Logins Followed by Post-Login Execution
  AN1638 Linux

  SSH login from a remote system (via sshd), followed by user context execution of suspicious binaries or privilege escalation behavior.

  auditd:EXECVE EXECVE → DC0032 Process Creation

  linux:syslog None → DC0067 Logon Session Creation

  NSM:Flow TCP port 22 traffic → DC0078 Network Traffic Flow

  Tunable: TimeWindow SuspiciousProcessList UsernameFilter
  AN1639 macOS

  SSH login detected via Unified Logs, followed by unusual process execution, especially outside normal user behavior patterns.

  macos:unifiedlog process = 'sshd' → DC0088 Logon Session Metadata

  macos:unifiedlog process = 'ssh' OR eventMessage CONTAINS 'ssh' → DC0085 Network Traffic Content

  macos:osquery process_events → DC0032 Process Creation

  Tunable: TimeWindow UserContext CommandLineKeywords
  AN1640 ESXi

  SSH login via hostd or /var/log/auth.log, followed by CLI access to host shell or file manipulation in restricted areas.

  esxi:auth None → DC0088 Logon Session Metadata

  esxi:shell None → DC0064 Command Execution

  esxi:vmkernel port 22 access → DC0078 Network Traffic Flow

  Tunable: AllowedUsers TimeWindow CommandList

Sigma rules tagged attack.t1021.004 (5)

T1059.004 Unix Shell primary impact

• DET0384 Behavioral Detection of Unix Shell Execution
  AN1081 Linux

  Detects bash, sh, zsh, or BusyBox shell execution initiated via remote sessions, unauthorized users, or embedded within secondary script interpreters. Focus is on chained behavior: shell > suspicious commands > network discovery or persistence indicators.

  auditd:SYSCALL execve → DC0032 Process Creation

  linux:osquery socket_events → DC0078 Network Traffic Flow

  linux:syslog auth.log / secure.log → DC0067 Logon Session Creation

  Tunable: ExecutableName UserContext ParentProcess TimeWindow CommandLinePattern
  AN1082 macOS

  Identifies use of sh/bash/zsh in suspicious context, such as user scripts launched from non-standard apps (e.g., Preview.app), embedded in LaunchDaemons, or executed outside Terminal.app. Looks for misuse in Automator, LaunchAgents, or NSAppleScript-executed shell.

  macos:unifiedlog log stream --predicate 'eventMessage contains "exec"' → DC0032 Process Creation

  macos:osquery launchd + process_events → DC0064 Command Execution

  macos:syslog system.log, asl.log → DC0029 Script Execution

  Tunable: ScriptLocation ParentProcess UserRole
  AN1083 ESXi

  Detects BusyBox or Ash shell execution from unauthorized logins or remote connections. Focus is on rare shell invocations from DCUI, SSH sessions, or remote management paths. Also watches for payload droppers or persistence artifacts using shell.

  esxi:vmkernel DCUI shell start, BusyBox activity → DC0064 Command Execution

  esxi:auth Shell login or escalation → DC0067 Logon Session Creation

  Tunable: UserContext CommandPattern ShellPath
  AN1084 Network Devices

  Detects Unix shell usage on network appliances (e.g., routers, firewalls, embedded Linux) through rare console commands, CLI interfaces, or script injection via exposed APIs or SSH.

  networkdevice:syslog CLI Command Audit → DC0064 Command Execution

  NSM:Flow remote access → DC0082 Network Connection Creation

  Tunable: Interface CommandString

Sigma rules tagged attack.t1059.004 (18)

All 18 rules on the technique page →

T1078 Valid Accounts exploitation technique

• DET0560 Detection of Valid Account Abuse Across Platforms
  AN1543 Windows

  Detection of compromised or misused valid accounts via anomalous logon patterns, abnormal logon types, and inconsistent geographic or time-based activity across Windows endpoints.

  WinEventLog:Security EventCode=4624 → DC0067 Logon Session Creation

  WinEventLog:Security EventCode=4776, 4625 → DC0002 User Account Authentication

  WinEventLog:Sysmon EventCode=1 → DC0032 Process Creation

  Tunable: LogonType TimeWindow GeoIPMismatch
  AN1544 Linux

  Detection of valid account misuse through SSH logins, sudo/su abuse, and service account anomalies outside expected patterns.

  auditd:SYSCALL execve → DC0032 Process Creation

  NSM:Connections sshd or PAM logins → DC0002 User Account Authentication

  Tunable: UserContext HostDensityThreshold LoginMethod
  AN1545 macOS

  Detection of interactive and remote logins by service accounts or users at unusual times, with unexpected child process activity.

  macos:unifiedlog loginwindow, sshd → DC0088 Logon Session Metadata

  macos:unifiedlog exec logs → DC0032 Process Creation

  Tunable: LoginOrigin ProcessTreeDepth
  AN1546 Identity Provider

  Detection of valid account abuse in IdP logs via geographic anomalies, impossible travel, risky sign-ins, and multiple MFA attempts or failures.

  saas:okta Sign-in logs / audit events → DC0002 User Account Authentication

  Tunable: MFAFailureCount RiskScoreThreshold IPGeoVelocity
  AN1547 Containers

  Detection of containerized service accounts or compromised kubeconfigs being used for cluster access from unexpected nodes or IPs.

  kubernetes:audit authentication.k8s.io → DC0002 User Account Authentication

  Tunable: ServiceAccountScope ClusterIPWhitelist

Sigma rules tagged attack.t1078 (56)

All 56 rules on the technique page →

T1133 External Remote Services exploitation technique

• DET0354 Behavior-chain detection for T1133 External Remote Services across Windows, Linux, macOS, Containers
  AN1004 Windows

  Unusual or unauthorized external remote access attempts (e.g., RDP, VPN, Citrix) → repeated failed logins followed by a successful session from uncommon geolocations or outside business hours → subsequent internal lateral movement or data exfiltration activities.

  WinEventLog:Security EventCode=4776, 4625 → DC0002 User Account Authentication

  WinEventLog:Application VPN, Citrix, or remote access gateway logs showing external IP addresses → DC0038 Application Log Content

  WinEventLog:Sysmon EventCode=3, 22 → DC0082 Network Connection Creation

  Tunable: BusinessHours KnownRemoteIPs FailedLogonThreshold GeoIPWhitelist TimeWindow
  AN1005 Linux

  Repeated SSH, VPN, or RDP gateway authentication attempts from external IPs → subsequent successful logon → remote shell or lateral movement activity (e.g., scp/sftp).

  auditd:SYSCALL ssh logins or execve of remote commands → DC0088 Logon Session Metadata

  NSM:Connections Failed password or accepted password for SSH users → DC0038 Application Log Content

  NSM:Flow connection: Inbound connections to SSH or VPN ports → DC0082 Network Connection Creation

  Tunable: KnownSSHClients FailedLogonThreshold TimeWindow
  AN1006 macOS

  Unexpected inbound or outbound VNC/SSH/Screen Sharing connections from external sources → repeated failed logins followed by success → remote interactive sessions or abnormal file transfers.

  macos:unifiedlog Remote login (ssh) or screen sharing authentication attempts → DC0088 Logon Session Metadata

  macos:unifiedlog Inbound connections to VNC/SSH ports → DC0082 Network Connection Creation

  PF:Logs External traffic to remote access services → DC0078 Network Traffic Flow

  Tunable: KnownVNCServers TimeWindow
  AN1007 Containers

  Connections to exposed container services (e.g., Docker API, Kubernetes API server) from unauthorized external IPs → abnormal container creation/start → lateral activity within cluster nodes.

  ApplicationLog:API Docker/Kubernetes API access from external sources → DC0038 Application Log Content

  kubernetes:audit Unauthorized container creation or kubelet exec logs → DC0088 Logon Session Metadata

  NSM:Flow External access to container ports (2375, 6443) → DC0082 Network Connection Creation

  Tunable: AllowedCIDRs TimeWindow

Sigma rules tagged attack.t1133 (20)

All 20 rules on the technique page →

T1588 Obtain Capabilities exploitation technique

• DET0850 Detection of Obtain Capabilities
  AN1982 PRE

  Consider use of services that may aid in the tracking of newly issued certificates and/or certificates in use on sites across the Internet. In some cases it may be possible to pivot on known pieces of certificate information to uncover other adversary infrastructure. Some server-side components of adversary tools may have default values set for SSL/TLS certificates. Much of this activity will take place outside the visibility of the target organization, making detection of this behavior difficult. Detection efforts may be focused on related stages of the adversary lifecycle, such as during Defense Evasion or Command and Control. Monitor for contextual data about a malicious payload, such as compilation times, file hashes, as well as watermarks or other identifiable configuration information. Much of this activity will take place outside the visibility of the target organization, making detection of this behavior difficult. Detection efforts may be focused on related stages of the adversary lifecycle, such as during Defense Evasion or Command and Control. Monitor for logged network traffic in response to a scan showing both protocol header and body values that may buy and/or steal capabilities that can be used during targeting. Much of this activity will take place outside the visibility of the target organization, making detection of this behavior difficult. Detection efforts may be focused on related stages of the adversary lifecycle, such as during Defense Evasion or Command and Control. Consider analyzing malware for features that may be associated with malware providers, such as compiler used, debugging artifacts, code similarities, or even group identifiers associated with specific Malware-as-a-Service (MaaS) offerings. Malware repositories can also be used to identify additional samples associated with the developers and the adversary utilizing their services. Identifying overlaps in malware use by different adversaries may indicate malware was obtained by the adversary rather than developed by them. In some cases, identifying overlapping characteristics in malware used by different adversaries may point to a shared quartermaster. Malware repositories can also be used to identify features of tool use associated with an adversary, such as watermarks in Cobalt Strike payloads.

  Certificate None → DC0093 Certificate Registration

  Malware Repository None → DC0003 Malware Metadata

  Internet Scan None → DC0104 Response Content

  Malware Repository None → DC0011 Malware Content

Sigma rules tagged attack.t1588 (2)