Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 c91a18b443c13e47…

MALICIOUS

RTF / .DOC

11.1 KB First seen: 2022-10-10
MD5: 84869eaeda27b8a63400803bf393071b SHA-1: 022a123ebf6e1af90cc0b0454e7da78afd28f9d0 SHA-256: c91a18b443c13e47d691c04d95617f9c029da410045a99cbe3de2ec243f21c79
220 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1059.005 Visual Basic T1566.001 Spearphishing Attachment

The sample is an RTF document that leverages the Equation Editor vulnerability (CVE-2017-11882) for execution. Heuristics indicate the presence of OLE object data and automatic linking, strongly suggesting exploitation. The document body contains a lure instructing the user to 'Enable editing', a common tactic for macro-based or exploit-based documents. The specific Equation Editor class 'eQUatION.3' is identified as a key indicator.

Heuristics 6

  • Equation Editor activation — CVE-2017-11882 related high CVE related CVE_2017_11882_ACTIVATION_RELATED
    RTF decodes to an Equation.3 ProgID and requests OLE activation with \objemb plus \objupdate. This reaches the legacy Equation Editor attack surface used by CVE-2017-11882/CVE-2018-0802 documents, but the malformed MTEF/native payload needed for stronger attribution was not recovered.
  • Split hex Equation Editor ProgID + OLE object critical RTF_EQUATION_EDITOR
    RTF embeds the Equation.3 ProgID as hex bytes near OLE object activation and splits the byte stream with whitespace or an ignorable RTF group. This is an Equation Editor OLE activation surface commonly used by CVE-2017-11882 / CVE-2018-0802 exploit documents.
  • Automatically linked OLE object high RTF_OBJAUTLINK
    RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
  • \objupdate forces OLE activation high RTF_OBJUPDATE
    RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
  • OLE object data medium RTF_OBJDATA
    RTF contains 1 \objdata section(s) — embedded OLE objects
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000018c1.bin
d0fbbf932f0e7736bbf66a207fd342d8202eadb6c617480305b3df5a5ba2d6d0		 rtf-objdata-decoded RTF \objdata at offset 0x18C1 1390 bytes

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