Malicious RTF — malware analysis report

Static analysis result for SHA-256 956e422a8c959d00…

MALICIOUS

RTF

3.99 MB First seen: 2021-06-30
MD5: 5a1f70c9e72e494e63998f22eef729ee SHA-1: e1c5224d113c7b38440fc0dc0642902c86a63066 SHA-256: 956e422a8c959d002d16fc205d144a509dd8bc67cc803cfdb89403e3fbbfc993
260 Risk Score

Malware Insights

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

The RTF file contains critical heuristics indicating the exploitation of CVE-2017-11882 via Microsoft Equation Editor. This exploit typically downloads and executes a secondary payload, making it a common initial vector for further compromise. The presence of OLE object data and excessive hex data further supports the payload delivery mechanism.

Heuristics 6

  • 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 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.
  • 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 ~4075KB 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_off000013de.bin rtf-objdata-decoded RTF \objdata at offset 0x13DE 1056618 bytes
SHA-256: 49c27e479570470c45324e0748ad5a5728ce95bf29394281580a523016a38070

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