Malicious RTF — malware analysis report

Static analysis result for SHA-256 ca88bc07598b37e8…

MALICIOUS

RTF

1.01 MB First seen: 2021-06-17
MD5: 615e95bff0e84e833a6de7caad6b4221 SHA-1: 9e8c982b2e853ec6d749e990876a96157ebeec6f SHA-256: ca88bc07598b37e8e2292f1a10e06c0adb7c898d3f3039e53b18d77d7db20105
180 Risk Score

Malware Insights

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

The RTF file contains embedded OLE objects, specifically triggering heuristics related to Equation Editor and CVE-2017-11882. The ".objupdate" directive forces the activation of these embedded objects, leading to the exploitation of the Equation Editor vulnerability. This indicates the file is designed to execute arbitrary code upon opening.

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_off00000f58.bin rtf-objdata-decoded RTF \objdata at offset 0xF58 46135 bytes
SHA-256: 1dbde16e1abc0642998ca99951ec0fbb49b024ced91a3a1b8221e84f22f4dbdc
objdata_01_off0002acb9.bin rtf-objdata-decoded RTF \objdata at offset 0x2ACB9 217076 bytes
SHA-256: faaa23976e44b1147dfaf4bfbddc4554674728770dee43f10bab0d524243535b

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