Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 b9cb9bec2eb7a34b…

MALICIOUS

RTF / .DOC

2.05 MB First seen: 2022-04-27
MD5: cbc59aaff371c7d8e7f60d4301801cb3 SHA-1: 0f14eb60937e90e317ac821a0fb9b4214a105281 SHA-256: b9cb9bec2eb7a34babd9d946a63bc67223bf62760aecf463bf466ae3aa919f87
180 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The file is an RTF document containing an embedded OLE object that exploits CVE-2017-11882 via the Equation Editor. The decoded object data suggests the presence of a Visual Basic script, likely intended to download and execute a second-stage payload. The RTF structure and the specific Equation Editor exploit point to a common delivery mechanism for malware.

Heuristics 5

  • 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.
  • Split hex Equation Editor ProgID + OLE object critical 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.
  • \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_off0000129e.bin
ab155ac9a54b28f20543cd70c96193ea0c0855cb616ebd794f1a5843d0ea795c		 rtf-objdata-decoded RTF \objdata at offset 0x129E 86019 bytes
objdata_01_off00036c06.bin
15b7f137c999929be510fea7aaa1c34a11c506a87bc2b1d42d45986f1d905f44		 rtf-objdata-decoded RTF \objdata at offset 0x36C06 457432 bytes

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