Office (OOXML) / .XLSX malware analysis — malicious · 5355a12b558956c3

MALICIOUS

Office (OOXML) / .XLSX

2.54 MB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 12.0000

MD5: bf5c6d3d640306027eafec85cc088f27 SHA-1: 279bceebf176e003e93585dd13bd9435bcc1abe9 SHA-256: 5355a12b558956c322aef1f158747f83b510b348ddf991a21d18593bdbe920fb

150 Risk Score

Malware Insights

MITRE ATT&CK

T1203 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 an anomaly in the Equation Editor's native stream, consistent with CVE-2018-0798, suggesting it's designed to exploit this vulnerability for client-side execution. The embedded object's Ole10Native stream appears to carry a payload.

Heuristics 6

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/oleObject1.bin 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
Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET

Excel workbook contains 1 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
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` `8e22bd7ec53043453551b95d3c0b6cc6d9d07fce2493df9302ea838f151eeee8`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oleObject1.bin	2386944 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.97, consistent with packed or encrypted content.
`ooxml_oleobject_00_ole10native_00.bin` `987b594ed3474637ca0e535630b79c0e3d942f3f10b25b6d6e2c5c23ee55a2ce`	ole-package	OOXML xl/embeddings/oleObject1.bin Ole10Native stream: oLE10NatIVe	2365644 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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