Office (OOXML) / .XLSX malware analysis — malicious · b19815b9d2f36641

MALICIOUS

Office (OOXML) / .XLSX

936.6 KB Created: 2021-09-22 12:07:42 UTC Authoring application: Microsoft Excel 12.0000

MD5: 83c23ce9359c563ef411033945a329dc SHA-1: a70567b554d98eb137c4c8061634e16261907e88 SHA-256: b19815b9d2f36641d41426292eb3e88fe049feeea18662e5f579d8d0452f56ea

140 Risk Score

Malware Insights

MITRE ATT&CK

T1204 Malicious Link T1204.001 Malicious Link: Malicious Link T1559 Component Object Model Hijacking T1559.001 Component Object Model Hijacking: Component Object Model Hijacking

The sample is an Excel document containing an embedded OLE object, specifically an Equation Editor object. High-severity heuristics indicate that this Equation Editor object is anomalous and carries a payload, strongly suggesting exploitation of CVE-2018-0798. This technique is commonly used to deliver second-stage malware. No document body or scripts were extracted, but the presence of the malicious OLE object is sufficient evidence.

Heuristics 4

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/VkJDOC.9gBb 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.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `d8c3f84791d6ebc9d1c8153a6592e46f5fed509d570e1a0fe083fe9c91d627c4`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/VkJDOC.9gBb	1272320 bytes
`ooxml_oleobject_00_ole10native_00.bin` `3c9e5316f5fc449a61c8e5022f1a14e1dbef7aa05a9987a79cefa64797312309`	ole-package	OOXML xl/embeddings/VkJDOC.9gBb Ole10Native stream: Ole10Native	1259802 bytes

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