Office (OOXML) / .XLSX malware analysis — malicious · a924bd7239e5c95f

MALICIOUS

Office (OOXML) / .XLSX

3.04 MB Created: 2021-04-28 21:02:36 UTC Authoring application: Microsoft Excel 12.0000

MD5: 750056c758ce9628cbe2a39d018264dd SHA-1: 2a3420b035948d89e4e4f9b7a5cf71d3224887ec SHA-256: a924bd7239e5c95f3116a195b5b34b733dcdbbcdd65d91465fc0d822dae1c8ac

142 Risk Score

Malware Insights

MITRE ATT&CK

T1204 Malicious Link T1204.001 Malicious Link: Malicious Link T1566 Phishing T1566.001 Phishing: Spearphishing Attachment T1566.002 Phishing: Spearphishing via Service

The file is an Excel spreadsheet containing an embedded OLE object, specifically an Equation Editor object. High-entropy anomalies within the Equation Editor's native stream indicate it is being used to deliver a malicious payload, likely exploiting CVE-2018-0798. No document body text or scripts were extracted, so the exact nature of the payload cannot be determined, but the exploit vector is clear.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/b8K7XBuQh.uk 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` `d6106ef48075c4beae28244634084e013cfcbe822a1ed0534b74bf69bda9a54a`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/b8K7XBuQh.uk	3511808 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.95, consistent with packed or encrypted content.
`ooxml_oleobject_00_ole10native_00.bin` `aeaf7212cd2d51ff52a3f0629f0ccc254dd431edb4cbb2eae1d8c12442f037fe`	ole-package	OOXML xl/embeddings/b8K7XBuQh.uk Ole10Native stream: Ole10Native	3481797 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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