Malicious RTF — malware analysis report

Static analysis result for SHA-256 5a097c4ee50a8950…

MALICIOUS

RTF

1.91 MB First seen: 2021-05-26
MD5: 6505468640e2216b81ee12cc2178a462 SHA-1: 8cd37260e5e72ae4e43f5132a48f8b2a62fad0f3 SHA-256: 5a097c4ee50a895003e11c9b420a44ff7f3462ee1c9a48f14629564d0af074fa
180 Risk Score

Malware Insights

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

The RTF document contains embedded OLE object data, specifically triggering the CVE-2017-11882 vulnerability through the Equation Editor. This exploit allows for the execution of arbitrary code, likely to download and run a secondary payload. The presence of multiple RTF-specific heuristics and the critical Equation Editor firing strongly indicate this exploit vector.

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 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000b13.bin rtf-objdata-decoded RTF \objdata at offset 0xB13 96726 bytes
SHA-256: 65cef27038d12cdc2cbd173577ab4377f084a9a8401edbb8fc70b2f72d8457df

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