Malicious RTF — malware analysis report

Static analysis result for SHA-256 91ee2a99d9bccbac…

MALICIOUS

RTF

1.01 MB First seen: 2021-06-13
MD5: 5086661dda0422cd0e1cf99e6fdc870d SHA-1: 079e6f4328cd2d4098c1273dadaa0f16f2e20abb SHA-256: 91ee2a99d9bccbacf0427b3edb77de82fe6f31ec9d194ac5fc6e40a744725805
180 Risk Score

Malware Insights

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

The RTF file contains embedded OLE objects, specifically triggering heuristics related to Equation Editor and CVE-2017-11882. The ".objupdate" directive forces the activation of these embedded objects, leading to the exploitation of the Equation Editor vulnerability. This indicates the file is designed to execute arbitrary code upon opening.

Heuristics 5

  • Split hex Equation Editor ProgID + OLE object critical CVE likely RTF_EQUATION_EDITOR
    RTF embeds the Equation.3 ProgID as hex bytes near OLE object activation and splits the byte stream with whitespace or an ignorable RTF group. This is an Equation Editor OLE activation surface commonly used by CVE-2017-11882 / CVE-2018-0802 exploit documents.
  • 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 2 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000f58.bin rtf-objdata-decoded RTF \objdata at offset 0xF58 48995 bytes
SHA-256: c5f63e2d9bc487501187d677bb0c05a711e2f6b68a02f5df81fc9c6934077ade
objdata_01_off0002a9cd.bin rtf-objdata-decoded RTF \objdata at offset 0x2A9CD 217076 bytes
SHA-256: faaa23976e44b1147dfaf4bfbddc4554674728770dee43f10bab0d524243535b

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