Malicious RTF — malware analysis report

Static analysis result for SHA-256 f9f927d4d30cfe9d…

MALICIOUS

RTF

10.9 KB First seen: 2020-09-07
MD5: 83481720160736a3dc94fedd81a90074 SHA-1: ba252f9e4cc1af7fafb3834bd42acf084063263e SHA-256: f9f927d4d30cfe9de81c9ecf705313b7308dda18e4be434fa4db68ca0d4db17e
200 Risk Score

Malware Insights

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

The RTF document contains an embedded OLE object that is automatically updated and activated, triggering the Equation Editor. Heuristics indicate this is related to CVE-2017-11882, a known vulnerability allowing for arbitrary code execution. The exploit likely serves as a dropper for a secondary malicious payload.

Heuristics 5

  • Obfuscated Equation Editor ProgID + activation critical CVE related RTF_EQUATION_EDITOR
    RTF decodes to an Equation.3 ProgID from top-level \objdata hex after nested RTF junk groups are ignored, and the document also contains \objemb plus \objupdate activation. This is an obfuscated Equation Editor exploit surface associated with CVE-2017-11882 / CVE-2018-0802 families, but no exact malformed MTEF CVE primitive was recovered from this object.
  • 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.
  • 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 1 \objdata section(s) — embedded OLE objects

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001b28.bin rtf-objdata-decoded RTF \objdata at offset 0x1B28 1830 bytes
SHA-256: 1ddbbad2610c1e70a21e1942ecc63744d8e15a9ca1ddb3be9ba7427dc295b819

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