Malicious RTF — malware analysis report

Static analysis result for SHA-256 fd72ce0da0e91b21…

MALICIOUS

RTF

1.96 MB First seen: 2021-07-02
MD5: 23574e5c06f518a31e4721c3832746e3 SHA-1: 6e1d8963752104d29cb9dc1bd0dd80dd0327c64f SHA-256: fd72ce0da0e91b2186c611bb8cee53dcd4691926d2a06f00f99f086e84e8734d
260 Risk Score

Malware Insights

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

The RTF file contains multiple indicators related to the Equation Editor vulnerability (CVE-2017-11882), including OLE object data and a decoded OLE1 object with a high entropy score. This strongly suggests the file is designed to exploit this vulnerability for client-side execution, likely delivered as a spearphishing attachment.

Heuristics 6

  • 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 OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED
    RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact 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.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~2055KB of hex-encoded data inside \objdata sections — may hide a payload
  • 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_off000000bc.bin rtf-objdata-decoded RTF \objdata at offset 0xBC 1027870 bytes
SHA-256: 03b35ebdf5c1c88f4f4c7f7e0156bff586dd0eef765d7399ae82d7b62d2e99a4

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