Coverage › CVE-2023-4966

CVE-2023-4966 Mapped Sigma

Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability

Vendor / product

Citrix — NetScaler ADC and NetScaler Gateway

Description (CISA)

Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for sensitive information disclosure when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.

Added to KEV

2023-10-18

Due date

2023-11-08

Required action

Apply mitigations and kill all active and persistent sessions per vendor instructions [https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/] OR discontinue use of the product if mitigations are unavailable.

Known ransomware use

Known

CWE

CWE-119

CISA notes

https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/, https://support.citrix.com/article/CTX579459/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20234966-and-cve20234967
https://nvd.nist.gov/vuln/detail/CVE-2023-4966

Elsewhere

cve.org · NVD · CISA KEV · JSON

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

3 mapping objects across 3 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

T1005 Data from Local System primary impact

• DET0380 Detection of Local Data Collection Prior to Exfiltration
  AN1070 Windows

  Adversaries collecting local files via PowerShell, WMI, or direct file API calls often include recursive file listings, targeted file reads, and temporary file staging.

  WinEventLog:Security EventCode=4688 → DC0032 Process Creation

  WinEventLog:Sysmon EventCode=11 → DC0039 File Creation

  Tunable: TargetFilePathRegex ParentProcessFilter
  AN1071 Linux

  Adversaries using bash scripts or tools to recursively enumerate user home directories, config files, or SSH keys.

  auditd:SYSCALL open → DC0055 File Access

  auditd:SYSCALL execve → DC0032 Process Creation

  Tunable: TimeWindow ScriptToolName
  AN1072 macOS

  Adversary use of bash/zsh or AppleScript to locate files and exfil targets like user keychains or documents.

  macos:unifiedlog process:spawn → DC0032 Process Creation

  fs:fsusage read/write → DC0055 File Access

  Tunable: UserContext TargetVolume
  AN1073 Network Devices

  Collection of device configuration via CLI commands (e.g., show running-config, copy flash, more), often followed by TFTP/SCP transfers.

  networkdevice:cli command logging → DC0064 Command Execution

  Tunable: CommandScope AuthenticatedUserList
  AN1074 ESXi

  Adversaries accessing datastore or configuration files via vim-cmd, esxcli, or SCP to extract logs, VMs, or host configurations.

  esxis:vmkernel Datastore Access → DC0055 File Access

  esxi:hostd Command Execution → DC0064 Command Execution

  Tunable: AccessPathRegex InteractiveShellUsage

Sigma rules tagged attack.t1005 (14)

T1134.001 Token Impersonation/Theft secondary impact

• DET0482 Behavior-chain detection for T1134.001 Access Token Manipulation: Token Impersonation/Theft on Windows
  AN1324 Windows

  Detection of token duplication and impersonation attempts by correlating suspicious command-line executions (e.g., runas) with API calls to DuplicateToken, DuplicateTokenEx, ImpersonateLoggedOnUser, or SetThreadToken. The chain includes the initial command execution or in-memory API invocation → token handle duplication or thread token assignment → a new or existing process assuming the impersonated user's context.

  WinEventLog:Security EventCode=4688 → DC0032 Process Creation

  WinEventLog:Sysmon EventCode=10 → DC0035 Process Access

  ETW:Token api_call: DuplicateTokenEx, ImpersonateLoggedOnUser, SetThreadToken → DC0021 OS API Execution

  Tunable: AllowedSystemProcesses TimeWindow UserContextFilter ParentProcessAnomalyThreshold

Sigma rules tagged attack.t1134.001 (9)

T1574 Hijack Execution Flow exploitation technique

• DET0218 Detection Strategy for Hijack Execution Flow across OS platforms.
  AN0609 Windows

  Unusual modifications to service binary paths, registry keys, or DLL load paths resulting in alternate execution flow. Defender observes registry key modifications, suspicious file writes into system directories, and processes loading libraries from abnormal paths.

  WinEventLog:Sysmon EventCode=1 → DC0032 Process Creation

  WinEventLog:Sysmon EventCode=7 → DC0016 Module Load

  WinEventLog:Security EventCode=4657 → DC0063 Windows Registry Key Modification

  WinEventLog:Sysmon EventCode=11 → DC0039 File Creation

  Tunable: ServiceBaseline AllowedDllPaths TimeWindow
  AN0610 Linux

  Adversary manipulation of shared library paths, environment variables, or replacement of service binaries. Defender observes suspicious modifications in /etc/ld.so.preload, service config changes, or file writes replacing existing executables.

  auditd:SYSCALL open/write syscalls targeting /etc/ld.so.preload or binaries in /usr/bin → DC0061 File Modification

  linux:syslog Service restart with modified executable path → DC0041 Service Metadata

  linux:osquery Process execution with LD_PRELOAD or modified library path → DC0032 Process Creation

  Tunable: MonitoredDirectories EnvVarMonitors
  AN0611 macOS

  Abuse of DYLD_INSERT_LIBRARIES or hijacking framework paths for malicious libraries. Defender observes processes invoking abnormal dylibs, modified plist files, or persistence entries pointing to altered binaries.

  macos:unifiedlog Execution of process with DYLD_INSERT_LIBRARIES set → DC0032 Process Creation

  macos:unifiedlog Modified application plist or binary replacement in /Applications → DC0061 File Modification

  macos:unifiedlog Dylib loaded from abnormal location → DC0016 Module Load

  Tunable: AllowedDylibPaths PlistMonitors

Sigma rules tagged attack.t1574 (8)

Sigma rules tagged with this CVE directly

4 rules carry cve.2023-4966.