Malicious RTF — malware analysis report

Static analysis result for SHA-256 692c4ad356a57f00…

MALICIOUS

RTF

9.7 KB First seen: 2023-01-09
MD5: 6f2a631711b59bae99ae8445b4de57db SHA-1: 3e5ec2213a5a1adec763b65221c448824c4c79b9 SHA-256: 692c4ad356a57f004792a9633b92f86a2d08ee84dd19c2bdce9c7021ab119f9a
220 Risk Score

Malware Insights

The sample is an RTF document that leverages the CVE-2017-11882 vulnerability by embedding an obfuscated Equation Editor object. This object is designed to be automatically activated upon opening the document, leading to the execution of a secondary payload. The document body contains a lure instructing the user to enable editing, a common tactic for macro-based malware.

Heuristics 6

  • 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
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001aee.bin
164efb74564d4e5200cc11250e90d2358db59336d3c288f715243b9a76c03c88		 rtf-objdata-decoded RTF \objdata at offset 0x1AEE 1473 bytes

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