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Detection rules › Sigma

Potential Atlassian Confluence CVE-2021-26084 Exploitation Attempt

Status
test
Severity
high
Log source
product windows, category process_creation
Author
Bhabesh Raj
Source
github.com/SigmaHQ/sigma

Detects spawning of suspicious child processes by Atlassian Confluence server which may indicate successful exploitation of CVE-2021-26084

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1190 Exploit Public-Facing Application
ExecutionT1059 Command and Scripting Interpreter

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

title: Potential Atlassian Confluence CVE-2021-26084 Exploitation Attempt
id: 245f92e3-c4da-45f1-9070-bc552e06db11
status: test
description: Detects spawning of suspicious child processes by Atlassian Confluence server which may indicate successful exploitation of CVE-2021-26084
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2021-26084
    - https://confluence.atlassian.com/doc/confluence-security-advisory-2021-08-25-1077906215.html
    - https://github.com/h3v0x/CVE-2021-26084_Confluence
author: Bhabesh Raj
date: 2021-09-08
modified: 2023-02-13
tags:
    - attack.initial-access
    - attack.execution
    - attack.t1190
    - attack.t1059
    - cve.2021-26084
    - detection.emerging-threats
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        # Monitor suspicious child processes spawned by Confluence
        ParentImage|endswith: '\Atlassian\Confluence\jre\bin\java.exe'
        CommandLine|contains:
            - 'certutil'
            - 'cmd /c'
            - 'cmd /k'
            - 'cscript'
            - 'curl'
            - 'ipconfig'
            - 'powershell'
            - 'pwsh'
            - 'regsvr32'
            - 'rundll32'
            - 'whoami'
            - 'wscript'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    ParentImage|endswith: '\Atlassian\Confluence\jre\bin\java.exe'
    CommandLine|contains:
        - 'certutil'
        - 'cmd /c'
        - 'cmd /k'
        - 'cscript'
        - 'curl'
        - 'ipconfig'
        - 'powershell'
        - 'pwsh'
        - 'regsvr32'
        - 'rundll32'
        - 'whoami'
        - 'wscript'

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
  • certutil corpus 12 (sigma 10, kusto 2)
  • cmd /c corpus 5 (sigma 5)
  • cmd /k corpus 4 (sigma 4)
  • cscript corpus 15 (sigma 15)
  • curl corpus 17 (sigma 14, elastic 2, splunk 1)
  • ipconfig corpus 4 (sigma 3, kusto 1)
  • powershell corpus 25 (sigma 24, chronicle 1)
  • pwsh corpus 7 (sigma 7)
  • regsvr32 corpus 15 (sigma 15)
  • rundll32 corpus 26 (sigma 23, chronicle 2, kusto 1)
  • whoami corpus 13 (sigma 9, splunk 2, elastic 1, kusto 1)
  • wscript corpus 16 (sigma 16)
ParentImageends_with
  • \Atlassian\Confluence\jre\bin\java.exe