Office (OOXML) / .XLSX malware analysis — malicious · 9f23628ed24a8b76

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 253be7f51c24f2eca0ab252711be637c SHA-1: 1efb51057e44b3cfdd982f4022e0cd652801ba0d SHA-256: 9f23628ed24a8b76376e7ff53c708a5ba99aa5b3d71001a434e64dc2727bded3

150 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1559.001 Component Object Model and Distributed Component Object Model

The sample is an Excel file containing an embedded OLE object, specifically identified as a Microsoft Equation Editor object. Heuristics indicate this object exploits CVE-2018-0798, a vulnerability associated with anomalous Equation Editor native streams. The object carries a payload-like Ole10Native stream with high entropy, suggesting it's designed to execute a secondary malicious component. No VBA or JavaScript macros were extracted, but the embedded OLE object is the primary vector for exploitation.

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 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`ooxml_oleobject_00.bin` `768ecf8fa0a5d6d8538f671ef8e334e23227c47544aa5b48f666b930e28ea1e7`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oleObject1.bin	2229760 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` `cf40876ea5ede8db6598c5f70eaa15f32287d740b7d061e85c8211938a4db774`	ole-package	OOXML xl/embeddings/oleObject1.bin Ole10Native stream: oLe10NaTivE	2209623 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.
`emf_00.emf` `6281596a02b7f58efbbd2fb63efbaacf781a5980d57748a4679791a8e61b5b6c`	ooxml-emf	OOXML EMF part: xl/media/image2.emf	498420 bytes

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