Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 c9b753173bdd1461…

MALICIOUS

RTF / .DOC

1.96 MB First seen: 2022-02-15
MD5: bfb2bb710820956c8f46c31109449345 SHA-1: 16b932867b03092c5098a41fa77b1f3d41dabb8d SHA-256: c9b753173bdd1461f93e415d400ccdcac75c991ab5f0f7ff52ac18ad518f49a8
180 Risk Score

Malware Insights

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

The file is an RTF document containing embedded OLE objects, specifically triggering the CVE-2017-11882 vulnerability via the Equation Editor. This exploit allows for the execution of arbitrary code embedded within the OLE object. The presence of ".\objupdate" and the critical RTF_EQUATION_EDITOR heuristic strongly indicate exploitation of this known vulnerability. The decoded object data, though truncated, contains VBA-like code that appears to be designed for further execution.

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_off00001347.bin
79bde8bdf16e9c44d4358a33ba25c730ab48e8176de6e8c78a1f5a71cf8c43cd		 rtf-objdata-decoded RTF \objdata at offset 0x1347 25584 bytes
objdata_01_off00019532.bin
689965aaaf88dfda2c46136e8ee45ccbdf5d380abcba88d5f9ff529d3c59ced2		 rtf-objdata-decoded RTF \objdata at offset 0x19532 463381 bytes

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