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Detection rules › Sigma

CVE-2023-38331 Exploitation Attempt - Suspicious WinRAR Child Process

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Nasreddine Bencherchali (Nextron Systems), Andreas Braathen (mnemonic.io)
Source
github.com/SigmaHQ/sigma

Detects exploitation attempt of CVE-2023-38331 (WinRAR before v6.23), where an attacker can leverage WinRAR to execute arbitrary commands and binaries.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1203 Exploitation for Client Execution

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: CVE-2023-38331 Exploitation Attempt - Suspicious WinRAR Child Process
id: ec3a3c2f-9bb0-4a9b-8f4b-5ec386544343
related:
    - id: e4556676-fc5c-4e95-8c39-5ef27791541f
      type: similar
status: test
description: Detects exploitation attempt of CVE-2023-38331 (WinRAR before v6.23), where an attacker can leverage WinRAR to execute arbitrary commands and binaries.
references:
    - https://www.group-ib.com/blog/cve-2023-38831-winrar-zero-day/
    - https://github.com/knight0x07/WinRAR-Code-Execution-Vulnerability-CVE-2023-38831/blob/26ab6c40b6d2c09bb4fc60feaa4a3a90cfd20c23/Part-1-Overview.md
author: Nasreddine Bencherchali (Nextron Systems), Andreas Braathen (mnemonic.io)
date: 2023-08-30
modified: 2024-01-22
tags:
    - detection.emerging-threats
    - attack.execution
    - attack.t1203
    - cve.2023-38331
logsource:
    category: process_creation
    product: windows
detection:
    selection_parent:
        ParentImage|endswith: '\WinRAR.exe'
    selection_folder:
        CommandLine|contains: '\AppData\Local\Temp\Rar$'
    selection_double_ext:
        CommandLine|re: '\.[a-zA-Z0-9]{1,4} \.'
    selection_binaries:
        # Note: add additional binaries that the attacker might use
        - Image|endswith:
              - '\cmd.exe'
              - '\cscript.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\wscript.exe'
        - OriginalFileName:
              - 'Cmd.Exe'
              - 'cscript.exe'
              - 'PowerShell.EXE'
              - 'pwsh.dll'
              - 'wscript.exe'
    condition: all of selection_*
falsepositives:
    - Unlikely
level: high

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_parent

selection_parent:
    ParentImage|endswith: '\WinRAR.exe'

Stage 2: selection_folder

selection_folder:
    CommandLine|contains: '\AppData\Local\Temp\Rar$'

Stage 3: selection_double_ext

selection_double_ext:
    CommandLine|re: '\.[a-zA-Z0-9]{1,4} \.'

Stage 4: selection_binaries

selection_binaries:
    - Image|endswith:
          - '\cmd.exe'
          - '\cscript.exe'
          - '\powershell.exe'
          - '\pwsh.exe'
          - '\wscript.exe'
    - OriginalFileName:
          - 'Cmd.Exe'
          - 'cscript.exe'
          - 'PowerShell.EXE'
          - 'pwsh.dll'
          - 'wscript.exe'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • \AppData\Local\Temp\Rar$
CommandLineregex_match
  • .[a-zA-Z0-9]{1,4} .
Imageends_with
  • \cmd.exe corpus 130 (sigma 130)
  • \cscript.exe corpus 73 (sigma 73)
  • \powershell.exe corpus 182 (sigma 182)
  • \pwsh.exe corpus 168 (sigma 168)
  • \wscript.exe corpus 75 (sigma 75)
OriginalFileNameeq
  • Cmd.Exe corpus 65 (sigma 43, splunk 17, elastic 5)
  • PowerShell.EXE corpus 120 (sigma 84, splunk 30, elastic 6)
  • cscript.exe corpus 19 (sigma 17, elastic 2)
  • pwsh.dll corpus 112 (sigma 79, splunk 30, elastic 3)
  • wscript.exe corpus 20 (sigma 17, elastic 3)
ParentImageends_with
  • \WinRAR.exe corpus 5 (sigma 5)