Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 f9b7a22e2775d5fd…

MALICIOUS

RTF / .DOC

1.91 MB First seen: 2022-03-28
MD5: eb220473b46c054a857536e32d4fc5a5 SHA-1: cec50f42983942f8b41b29757dc3db8bcf73ca34 SHA-256: f9b7a22e2775d5fde401ee400235e34897c7e4284f75c637bbb8a6bd55d1156a
220 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.003 Windows Command Shell

The file is an RTF document containing OLE object data, specifically triggering the CVE-2017-11882 vulnerability related to the Equation Editor. The presence of a large amount of hex-encoded data within the OLE object suggests it is hiding a payload. The ".objupdate" directive forces OLE activation, indicating an attempt to execute the embedded exploit. The decoded OLE object's native payload is associated with CVE-2017-11882, which is known to be used for arbitrary code execution.

Heuristics 5

  • Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED
    RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact 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.
  • \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.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1993KB of hex-encoded data inside \objdata sections — may hide a payload
  • OLE object data medium RTF_OBJDATA
    RTF contains 2 \objdata section(s) — embedded OLE objects

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001498.bin
4310b21136ede919c479a81b066d5bf1ae8c5313cbda4e4b503ad704673703ed		 rtf-objdata-decoded RTF \objdata at offset 0x1498 996745 bytes

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