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

Static analysis result for SHA-256 b7ec359d9ce5edd9…

MALICIOUS

Office (OOXML) / .XLSX

691.9 KB Created: 2021-02-03 07:57:22 UTC Authoring application: Microsoft Excel 15.0300
MD5: 34ea341a86ef62ca56e400e0df97f3c5 SHA-1: 1f4e17d70b8ce0af1887457f85f8bf96aa7f05ba SHA-256: b7ec359d9ce5edd99910dc32f7a07ad50dd056fb26791a6aed260a65b6cb684d
140 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter T1071.001 Application Layer Compromise T1566.001 Phishing

The analysis reveals a malformed Equation Editor OLE object embedded within the OOXML file. The presence of the Equation Editor CLSID, combined with anomalous native stream data and a large, high-entropy Ole10Native stream, strongly suggests exploitation of CVE-2018-0798. The file likely attempts to execute arbitrary code via this vulnerability. The embedded OLE objects are a common delivery mechanism for malicious payloads. The document excerpt details the exploitation of the Equation Editor component, confirming the intent.

Heuristics 4

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/4F3qK4.Em2Q 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
608b8b2637649666b4c76eb8422c136c82faadec1d58162a7324ccd53b470962		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/4F3qK4.Em2Q 982016 bytes
ooxml_oleobject_00_ole10native_00.bin
a841dbb8d19cced25eb6cdadd4c3ff8f89447c0ddc6b322eacb91641eee7afff		 ole-package OOXML xl/embeddings/4F3qK4.Em2Q Ole10Native stream: OLe10nAtiVe 971801 bytes

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