Malicious RTF — malware analysis report

Static analysis result for SHA-256 c95ff5833d97e67e…

MALICIOUS

RTF

2.18 MB First seen: 2021-10-01
MD5: 9786e1d1cf7e26e9d4e056a34782240f SHA-1: 71dae900c2c12a8fd21b91af64f7b6966489e081 SHA-256: c95ff5833d97e67edc83ea95bd1ee24aa1feeedc018f534d0e6eb84a7b8022c5
180 Risk Score

Malware Insights

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

The sample is an RTF document that contains embedded OLE objects, specifically triggering heuristics related to the Equation Editor vulnerability (CVE-2017-11882). This vulnerability allows for arbitrary code execution when the embedded object is activated. The presence of ".objupdate" further indicates an attempt to force OLE activation. The document body appears to contain obfuscated JavaScript-like code, likely part of the exploit chain.

Heuristics 5

  • 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.
  • \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
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000011e1.bin rtf-objdata-decoded RTF \objdata at offset 0x11E1 43157 bytes
SHA-256: 7667fd0182ea7c40362884b03d74567ed935416c88eb6f8019847e74e132c685
objdata_01_off0002614b.bin rtf-objdata-decoded RTF \objdata at offset 0x2614B 543771 bytes
SHA-256: 1dff60c32303d58fd426d1215689e547377c88210d425e277a4a202bc2e03050

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