Malicious RTF — malware analysis report

Static analysis result for SHA-256 2bc3b48093eed421…

MALICIOUS

RTF

3.7 KB First seen: 2021-05-23
MD5: b2fee098b852d4cce885c73c426d82fc SHA-1: cd11d5353c36ee35b76bdb1324e03beb6779df7d SHA-256: 2bc3b48093eed421b47e8413d3dd3b6d3b5cfa38d3100d999e4cc1816d76aef2
200 Risk Score

Malware Insights

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

The RTF file contains multiple indicators of exploitation for CVE-2017-11882, specifically related to the Equation Editor. The presence of OLE objects and the explicit firing of the RTF_EQUATION_EDITOR heuristic strongly suggest this vulnerability is being leveraged. This technique is commonly used to achieve arbitrary code execution, likely as a precursor to downloading 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.
  • Automatically linked OLE object high RTF_OBJAUTLINK
    RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
  • \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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000000a9.bin rtf-objdata-decoded RTF \objdata at offset 0xA9 1688 bytes
SHA-256: 575e437db02961bb57234c98aa35e9d6b3e9e22af8c72ad7bd9d32062b1aafbe

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