Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 db5e8202690e0ab4…

MALICIOUS

RTF / .DOC

1.80 MB First seen: 2022-04-11
MD5: 4c5dd21ffcef7049e7ba332af0973b57 SHA-1: 2251693deac3a204b0cd4a0bb77a4b0240de0e06 SHA-256: db5e8202690e0ab40149c24bd3796022975d9664d85324e706471428fae469f3
220 Risk Score

Malware Insights

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

The sample is an RTF document that leverages the Equation Editor vulnerability (CVE-2017-11882) to execute a payload. The presence of OLE object data and specific RTF heuristics strongly indicate this exploit. The decoded OLE object is a native payload, likely a secondary stage downloader or stealer, though its exact function cannot be determined without further analysis of the dropped payload.

Heuristics 5

  • Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED
    RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact 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.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1883KB of hex-encoded data inside \objdata sections — may hide a payload
  • OLE object data medium RTF_OBJDATA
    RTF contains 2 \objdata section(s) — embedded OLE objects

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001cd9.bin
9346924383c0eb7fce28c317fe2ac9801c19f00606dc0880dc6d9811a50a0b2c		 rtf-objdata-decoded RTF \objdata at offset 0x1CD9 941856 bytes

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