Malicious RTF — malware analysis report

Static analysis result for SHA-256 fbdadc7929c86b3d…

MALICIOUS

RTF

32.3 KB First seen: 2021-08-20
MD5: 55b1d80963dfc7ecf1366e79edc7b583 SHA-1: a454818ef4672e057205653c3ae64fc4810e8d40 SHA-256: fbdadc7929c86b3d34ea1220557d16b4a5adb6bdfd23218cefacc5f50e85f4f2
200 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of exploiting the CVE-2017-11882 vulnerability through Microsoft Equation Editor. The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_ACTIVATION_RELATED` heuristics strongly suggests this exploit. The `RTF_OBJAUTLINK` and `RTF_OBJUPDATE` heuristics indicate that the embedded OLE object is designed to be activated, leading to code execution. This is a common method for delivering secondary payloads, hence the high confidence in the attack pattern.

Heuristics 5

  • Split hex Equation Editor ProgID + OLE object critical CVE likely 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.
  • 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.
  • 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 2 \objdata section(s) — embedded OLE objects

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001633.bin rtf-objdata-decoded RTF \objdata at offset 0x1633 1824 bytes
SHA-256: 93d905bb56bfb5cc62580e1286f2628e83062b079b47ea5df71c49c3038929b9

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