Office (OOXML) / .XLSX malware analysis — malicious · b8b509a03643e795

MALICIOUS

Office (OOXML) / .XLSX

1.52 MB Created: 2021-09-22 12:07:42 UTC Authoring application: Microsoft Excel 12.0000

MD5: 71ba147565071da166cd1dfd13950efd SHA-1: 514477f6461dfacfd5685f979a89e7cd3f94b88e SHA-256: b8b509a03643e795ab01342047385d9780efda93fc0ba6875976caeec5a43843

142 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1204.002 Malicious File

The sample is a malicious Excel file containing an embedded OLE object, specifically identified as an Equation Editor object. Heuristics indicate this object exploits CVE-2018-0798, a vulnerability in the Equation Editor. The embedded object's Ole10Native stream exhibits high entropy and a payload-like structure, strongly suggesting it's designed to execute a secondary payload upon opening the document. No document body or scripts were extracted, but the exploit vector is clear.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/JV.JjwfKxd 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
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `f17e635266392d540f8ef9a63f533fe543612032dab6ff19188143a34183bd7a`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/JV.JjwfKxd	1844224 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.98, consistent with packed or encrypted content.
`ooxml_oleobject_00_ole10native_00.bin` `517106ff111113774c5e00c9122a179e817589ab8303e3a8d156d56918c0d948`	ole-package	OOXML xl/embeddings/JV.JjwfKxd Ole10Native stream: Ole10Native	1826888 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.

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