Malicious RTF — malware analysis report

Static analysis result for SHA-256 3e5acccb6f5f72b6…

MALICIOUS

RTF

1.86 MB First seen: 2021-09-29
MD5: 3a89cb368d29c2d72847e555d13f4b1c SHA-1: 78596d60d6f2336062ca3dfee5fffc6c93d31339 SHA-256: 3e5acccb6f5f72b657813017ee95fedf4adb94e8344f5391393edc7dc879c8d4
260 Risk Score

Malware Insights

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

The RTF file contains embedded OLE object data, specifically related to Equation Editor. Critical heuristics indicate a high likelihood of exploitation for CVE-2017-11882, which is known to deliver a second-stage payload. The excessive hex data and OLE object activation further support this attack vector.

Heuristics 6

  • 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.
  • 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.
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~1950KB 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_off00000098.bin rtf-objdata-decoded RTF \objdata at offset 0x98 975403 bytes
SHA-256: ff1f3f540a694d0747ceb0a57e52402759d599e509534dec02385885f2a05a81

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