Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 139caf726cd0e8bd…

MALICIOUS

RTF / .DOC

3.7 KB First seen: 2022-03-15
MD5: b337b161ec36f64c2bc64a241974bd76 SHA-1: 3157d5bf6682932b812e0e4f680d8db92dd213b2 SHA-256: 139caf726cd0e8bdd5d0e244c2f34a926662f67833253a33822bf73e088f7f59
180 Risk Score

Malware Insights

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

The RTF document contains embedded OLE objects, specifically triggering the CVE-2017-11882 vulnerability related to the Equation Editor. This exploit allows for arbitrary code execution upon activation, likely leading to the download and execution of a secondary payload. The presence of multiple OLE object-related heuristics and the specific CVE firing strongly indicate this attack vector.

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 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off000000d2.bin
3dbf51dbe23af8c09b1e03711bad434f8cfcda0ebfaceb733221025a53963911		 rtf-objdata-decoded RTF \objdata at offset 0xD2 1564 bytes

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