Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 3d796ca87d1d48da…

MALICIOUS

RTF / .DOC

2.21 MB
MD5: 884178d61e8bb9cac7da8b7b8e56db63 SHA-1: 2914a34d748d2ebefb61ff0f0f8d72da50f72db6 SHA-256: 3d796ca87d1d48da7dad8e64d28950ea7a680efa898a882f517f16eba3d63903
180 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.003 Windows Command Shell

The sample is an RTF document containing an embedded OLE object that leverages the Equation Editor vulnerability (CVE-2017-11882). The presence of RTF_EQUATION_EDITOR and CVE_2017_11882_ACTIVATION_RELATED heuristics strongly indicates exploitation of this known Microsoft Office vulnerability. The objupdate directive forces OLE object activation, leading to arbitrary code 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_off00001202.bin
bdc60af73994ded9662d15aa9542427b9ab341032bc1bac936b1fda16985d84e		 rtf-objdata-decoded RTF \objdata at offset 0x1202 27140 bytes
objdata_01_off0001c9c9.bin
1a9daf7f5259077ae9a7fba5e35fb7f5d70b6d43574b5a4ed8dc4e9c9ad184d1		 rtf-objdata-decoded RTF \objdata at offset 0x1C9C9 475057 bytes

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