Malicious RTF — malware analysis report

Static analysis result for SHA-256 86618518ff796dca…

MALICIOUS

RTF

1.60 MB First seen: 2022-05-18
MD5: bc4c675cb9ff8c4df32caeea668ebb44 SHA-1: 25e348327ad1f8b8f0a40406fe7337dc778564d3 SHA-256: 86618518ff796dca429e7eedbb97b9859c7cc3371b41ac51ebd8b03599496640
180 Risk Score

Malware Insights

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

The RTF file contains embedded OLE objects, specifically triggering the CVE-2017-11882 vulnerability related to Equation Editor. The presence of ".\objupdate" and the ProgID "Equation.3" strongly indicate exploitation of this known Microsoft Office vulnerability. This technique is commonly used to deliver secondary payloads, hence the high confidence in exploitation for client 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_off0000129e.bin
9fc30687f1d8bd14523377bd07e696e9c995b7c946e05cf5e54e0e6beeb380e7		 rtf-objdata-decoded RTF \objdata at offset 0x129E 85950 bytes
objdata_01_off00036b7c.bin
8e116a0d8fc7d726f18d93d20793e8dd4ce118f2355f86e148c399ba0c1b5e30		 rtf-objdata-decoded RTF \objdata at offset 0x36B7C 345139 bytes

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