Malicious RTF — malware analysis report

Static analysis result for SHA-256 7213a2ae550b01cd…

MALICIOUS

RTF

1.63 MB First seen: 2021-05-29
MD5: 8b030109be23bd6faf2fe8793a61d0f1 SHA-1: ec043716548aacdecd8a0a5a1e876524653f6ed5 SHA-256: 7213a2ae550b01cda777933bb9bb0b6ccde5ca3cd34ccbd4557209fe916dd5b1
240 Risk Score

Malware Insights

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

The RTF document contains multiple indicators of malicious activity, including the presence of OLE objects and excessive hex data, strongly suggesting the exploitation of CVE-2017-11882 via Microsoft Equation Editor. This vulnerability is commonly used to deliver a second-stage payload, likely an executable, which is then run on the victim's machine. The presence of the CVE-2017-11882 related heuristic confirms 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.
  • \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 ~1703KB 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
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000f27.bin rtf-objdata-decoded RTF \objdata at offset 0xF27 852009 bytes
SHA-256: c9cc9c549abaed9c3ade42850543753e52fc2b9925fd9394078122b296977af4

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