Malicious RTF — malware analysis report

Static analysis result for SHA-256 d5aa441a5dfb4acb…

MALICIOUS

RTF

1.82 MB First seen: 2021-07-02
MD5: fcadc904b298f62f1fb9168eeba1ba33 SHA-1: c1b81a7e15bca582e1fbd80975104432ef5caf6f SHA-256: d5aa441a5dfb4acbfc94b8659216a892281e817a589b49c0efc4edf818ebe914
180 Risk Score

Malware Insights

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

The RTF file contains embedded OLE objects and specifically triggers the CVE-2017-11882 vulnerability related to Microsoft Equation Editor. This exploit allows for the execution of arbitrary code, likely to download and run a secondary payload. The presence of ".objupdate" further indicates an attempt to force OLE object activation.

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.
  • \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 50054 bytes
SHA-256: 7d5d8542d0c323a18e0a8c6bc1f622850a77d35500cc4dc93b8d11591287369b
objdata_01_off0002f171.bin rtf-objdata-decoded RTF \objdata at offset 0x2F171 469226 bytes
SHA-256: 7d01ee387216102daeabf80a57c8f0d8112fdee1d8864b417a3fb9d69aa1d0dd

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