Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 5c131d192bb0f863…

MALICIOUS

RTF / .DOC

4.5 KB
MD5: a375d041d35259be20a45fdfbd966085 SHA-1: b618e6418c4b235c9deb58d7741a0cc3ce04ab2e SHA-256: 5c131d192bb0f86309fb424ecd58f929aee48a3244b3a49ce6a8422158b7a154
180 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 triggers the Equation Editor, specifically leveraging CVE-2017-11882. This vulnerability allows for the execution of arbitrary code upon activation, likely to download and run a secondary payload. The presence of RTF_OBJDATA, RTF_OBJEMB, RTF_EQUATION_EDITOR, CVE_2017_11882_ACTIVATION_RELATED, and RTF_OBJUPDATE heuristics strongly indicates this exploit.

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.
  • \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
  • 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_off0000004c.bin
92f1a2b2356daee35d44a64c079946126647fc0a4f0c6190e1611d4ed21b9c3b		 rtf-objdata-decoded RTF \objdata at offset 0x4C 2128 bytes

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