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

Static analysis result for SHA-256 43991fd2e81e6834…

MALICIOUS

Office (OOXML) / .XLSX

752.1 KB Created: 2021-09-22 12:07:42 UTC Authoring application: Microsoft Excel 12.0000
MD5: f66c844f67bf22518a8a108ca6534230 SHA-1: 27b9a6a507cd006151f5bcab842c7daccda236d7 SHA-256: 43991fd2e81e68346e4d93a18d6584b21264f4d4118671c5fe9a111a9693bdc8
100 Risk Score

Malware Insights

MITRE ATT&CK
T1566.002 Spearphishing Attachment T1204.001 Malicious Link

The sample is an Office document containing an embedded OLE object, specifically identified as a Equation Editor object. High-severity heuristics indicate that this Equation Editor object carries a payload-like Ole10Native stream with an anomalous size and entropy, strongly suggesting it's being used to deliver a secondary exploit or payload. This is a common technique for exploiting the Equation Editor vulnerability (CVE-2017-11882) to achieve arbitrary code execution.

Heuristics 3

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/o5WcYiB6t.BJ contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • 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
5c4d22cf7591d7428e78e24397188223ceeb85d45e44aa9daedaee7e1bad523f		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/o5WcYiB6t.BJ 1010176 bytes
ooxml_oleobject_00_ole10native_00.bin
f260f881884f26d41fcea050af0a313f7c6bef434bd17e8401857358d9790b37		 ole-package OOXML xl/embeddings/o5WcYiB6t.BJ Ole10Native stream: Ole10NAtIve 999685 bytes

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