Malicious RTF — malware analysis report

Static analysis result for SHA-256 cd75efbf860eced4…

MALICIOUS

RTF

1.75 MB First seen: 2021-05-26
MD5: 090eca63491230e20af2fbf3e3a02020 SHA-1: 671a6732afb7b103e183baffa6964f9d0a24475b SHA-256: cd75efbf860eced4a902532a3fa8488b56aae40c95ef101fff6e723a80d24cbe
220 Risk Score

Malware Insights

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

The RTF file contains critical heuristics indicating the exploitation of CVE-2017-11882 via an embedded OLE object within the Equation Editor. The presence of large, hex-encoded data blocks and the \objupdate directive strongly suggest that this object is a disguised payload designed to be executed upon activation. The file's structure and the specific exploit targeted point towards a malicious document designed for initial compromise.

Heuristics 5

  • 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.
  • 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.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1831KB 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_off000014b4.bin rtf-objdata-decoded RTF \objdata at offset 0x14B4 915897 bytes
SHA-256: 6107ceb6efce3ce970d89210a375b5d332d6e23fd5b4f88b388709911f9b4321

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