Malicious RTF — malware analysis report

Static analysis result for SHA-256 bac32ad4e656df1b…

MALICIOUS

RTF

40.9 KB First seen: 2023-02-13
MD5: e811ba615778cdce0ce22906862703ff SHA-1: 748b9199e5de4026f615a91e1612602db5186c34 SHA-256: bac32ad4e656df1b774dddfe1d3097f3df6dd811718f217941d2085e7e2ada93
200 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 User Execution: Malicious File T1059.005 PowerShell

The sample is an RTF document containing an embedded OLE object specifically identified as related to CVE-2017-11882, a known vulnerability in Microsoft Equation Editor. The presence of `RTF_EQUATION_EDITOR`, `CVE_2017_11882_ACTIVATION_RELATED`, and `RTF_OBJUPDATE` heuristics strongly indicates exploitation of this vulnerability. The document also contains a lure instructing the user to 'Enable editing', a common tactic to bypass security measures and trigger the exploit.

Heuristics 6

  • 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 1 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00004bb9.bin
66dda2cc8d499713ce9802ac729f771fc4c20af9b6464e49f63b11e9e1ff5740		 rtf-objdata-decoded RTF \objdata at offset 0x4BB9 1860 bytes

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