Malicious RTF — malware analysis report

Static analysis result for SHA-256 0cdf27422eeb9c92…

MALICIOUS

RTF

5.5 KB First seen: 2019-08-04
MD5: bcd0a8e6faa7a387be7b94408e36599c SHA-1: 11a9d25980b8f2874cac535748e04ac0fccde596 SHA-256: 0cdf27422eeb9c9286cf28b1839677c67aee28729b10ffbe1574bf051b7f9a34
200 Risk Score

Malware Insights

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

The RTF file contains evidence of exploitation targeting CVE-2017-11882 via the Equation Editor component. The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_ACTIVATION_RELATED` heuristics strongly indicates this vulnerability is being leveraged. This technique is commonly used to deliver secondary payloads, hence the likely attack pattern.

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_off00000b1a.bin rtf-objdata-decoded RTF \objdata at offset 0xB1A 1383 bytes
SHA-256: 2e4ea91af08825a5269e442bafdf96d15d9166a28df86a07f91ace3426645139

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