Potential Atlassian Confluence CVE-2021-26084 Exploitation Attempt

Status: test
Severity: high
Log source: category process_creation, product windows
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

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application
Execution	`T1059` Command and Scripting Interpreter

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

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

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`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 19 (sigma 14, elastic 4, 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 16 (sigma 9, elastic 4, splunk 2, kusto 1) `wscript` corpus 16 (sigma 16)	`field:"CommandLine" kind:match`
`ParentImage`	ends_with	`\Atlassian\Confluence\jre\bin\java.exe`	`field:"ParentImage" kind:ends_with value:"\Atlassian\Confluence\jre\bin\java.exe"`

Potential Atlassian Confluence CVE-2021-26084 Exploitation Attempt

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`