Malicious RTF — malware analysis report

Static analysis result for SHA-256 fcc4db48e9d11331…

MALICIOUS

RTF

1.57 MB First seen: 2022-09-14
MD5: b238f34870a8039dcb81348d203a1728 SHA-1: c78a583646753923569180b64185cd311cae100e SHA-256: fcc4db48e9d11331da3a6d8c4a78cefdaddede412bb548d4b9d5529c706acb90
180 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The RTF document contains embedded OLE objects, specifically triggering the CVE-2017-11882 vulnerability related to Equation Editor. The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_ACTIVATION_RELATED` heuristics strongly indicates exploitation of this known vulnerability. The `RTF_OBJUPDATE` heuristic suggests that the OLE object is configured to activate automatically, leading to the execution of a secondary payload.

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_off00001291.bin
54ab6322c9735a7912c6df3319d712a870e9eabd5c8ac3414903be980b50d851		 rtf-objdata-decoded RTF \objdata at offset 0x1291 80834 bytes
objdata_01_off0002eb86.bin
f7b929ce489dfb0e55f3383a35fdd691eace09a148b71bdce40ecf74b197fdc5		 rtf-objdata-decoded RTF \objdata at offset 0x2EB86 346461 bytes

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