Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 5b8ba81488fcf8cc…

MALICIOUS

RTF / .DOC

8.7 KB First seen: 2023-01-19
MD5: d7dfa99fc9e877210bcde1e8bb7f337d SHA-1: c0c5ad44ba564ef120d17d78555e604dbb73d7a3 SHA-256: 5b8ba81488fcf8cc7b57f9056f4a47bd50838591bf1ef6f46a3f73c264a4eea7
200 Risk Score

Malware Insights

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

The RTF document contains an embedded OLE object that triggers CVE-2017-11882, a known vulnerability in Microsoft Equation Editor. This exploit allows for arbitrary code execution, indicating a malicious intent to compromise the user's system. The presence of RTF_OBJDATA, RTF_OBJAUTLINK, RTF_EQUATION_EDITOR, and RTF_OBJUPDATE heuristics strongly supports this attack vector.

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_off000013b8.bin
e86a3f6d092cbf47c455368ba4bd143f0cf38e7f10ad984f6a3cb0247390607e		 rtf-objdata-decoded RTF \objdata at offset 0x13B8 1884 bytes

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