Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 1cd7833c7f9acb6d…

MALICIOUS

Office (OOXML) / .XLSX

748.9 KB Created: 2021-02-03 07:57:22 UTC Authoring application: Microsoft Excel 15.0300
MD5: 6c12ea90325ceb07e566ebd3d2da3901 SHA-1: c18521c804bccaf951a7e56dacb31a2da0e87e68 SHA-256: 1cd7833c7f9acb6db9d49a88fedbefd9888eb89b47c9137eff5b32ff9fb56b79
140 Risk Score

Malware Insights

MITRE ATT&CK
T1204 Malicious File T1204.002 Malicious File: Exploitation for Client Execution

The sample is an Excel file containing an embedded OLE object, specifically identified as a vulnerable Equation Editor object. Heuristics indicate anomalies in the Equation Editor's native stream, consistent with exploitation of CVE-2018-0798. This vulnerability allows for the execution of arbitrary code, likely to download and run a secondary payload.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/rnnS.rZYa contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • CVE-2018-0798 — anomalous Equation Editor native stream high CVE likely CVE_2018_0798_EQUATION_NATIVE_ANOMALY
    Embedded Equation Editor OLE data contains anomalous native stream bytes consistent with a CVE-2018-0798-style Equation Editor exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like, but it does not match the exact public matrix-overflow byte signature.
  • Equation Editor object carries payload-like Ole10Native stream high OLE_EQUATION_OLE10NATIVE_PAYLOAD_ANOMALY
    Embedded OLE object declares the Equation Editor CLSID but stores a large high-entropy Ole10Native stream with malformed package sizing. This is an exploit-shaped Equation/OLE payload container seen in malicious OOXML samples. It is not assigned to a specific CVE unless the MTEF/Equation Native primitive also matches.
  • Embedded OLE object medium OOXML_OLE_OBJECT
    Document contains an embedded OLE object

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
b2137655d31374a9e114403c0bf113a55922147303bcb33ce8c6a8edcc74f27b		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/rnnS.rZYa 1052672 bytes
ooxml_oleobject_00_ole10native_00.bin
1ac4a53ade3ae95616fef88e3d67a2abc7340f5fb7b0159e4d001e92992b8d20		 ole-package OOXML xl/embeddings/rnnS.rZYa Ole10Native stream: OLe10native 1041607 bytes

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