Office (OOXML) / .XLSX malware analysis — malicious · f5c6fbc178a815d5

MALICIOUS

Office (OOXML) / .XLSX

1.47 MB Created: 2021-09-22 12:07:42 UTC Authoring application: Microsoft Excel 12.0000 First seen: 2022-04-11

MD5: 055d68f95a1fdc4bfd0419a37e608086 SHA-1: 67840125e3b26872184edecfd2a805b44b51a329 SHA-256: f5c6fbc178a815d5b5d6efc33746180ab8d7cc9a68c47571ac344ca461437fa5

142 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1027 Obfuscated Files or Information

The sample is an Excel file 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, likely exploiting CVE-2018-0798. The embedded artifact 'xl/embeddings/oFlb9kuVh.zag' is identified as the carrier of this malicious payload. The exact nature of the payload is not discernible from static analysis alone, but the exploit mechanism is clear.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/oFlb9kuVh.zag 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` `90d3d0750715c4ff75434ac9781b7a77a6de57d29fb833df216cf5ea476f2eb3`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/oFlb9kuVh.zag	1856512 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` `a0e35739817cec58436c3ed20fc0e57047163df31568a5e85e2791aad070314b`	ole-package	OOXML xl/embeddings/oFlb9kuVh.zag Ole10Native stream: Ole10Native	1839237 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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