CVE-2021-26858 Exchange Exploitation

Detects possible successful exploitation for vulnerability described in CVE-2021-26858 by looking for creation of non-standard files on disk by Exchange Server’s Unified Messaging service which could indicate dropping web shells or other malicious content

title: CVE-2021-26858 Exchange Exploitation
id: b06335b3-55ac-4b41-937e-16b7f5d57dfd
status: test
description: |
    Detects possible successful exploitation for vulnerability described in CVE-2021-26858 by looking for
    creation of non-standard files on disk by Exchange Server’s Unified Messaging service
    which could indicate dropping web shells or other malicious content
references:
    - https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
author: Bhabesh Raj
date: 2021-03-03
modified: 2022-10-09
tags:
    - attack.t1203
    - attack.execution
    - cve.2021-26858
    - detection.emerging-threats
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith: 'UMWorkerProcess.exe'
    filter:
        TargetFilename|endswith:
            - 'CacheCleanup.bin'
            - '.txt'
            - '.LOG'
            - '.cfg'
            - 'cleanup.bin'
    condition: selection and not filter
falsepositives:
    - Unknown
level: high

• T1203Exploitation for Client Execution

• https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/↗