Office (OOXML) / .XLSX malware analysis — malicious · 281d5d2e057a2ecc

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: caa7649ae24eafae30470a408b885c49 SHA-1: d73e639c9e2d8bc4bef809d2aea88e820be04b94 SHA-256: 281d5d2e057a2ecca94356372c1aa859fbbcd42db008ba2be42b85586f1b39b6

142 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1027 Obfuscated Files or Information

The sample is an Office Open XML (OOXML) XLSX file containing an embedded OLE object, specifically a Microsoft Equation Editor object. Heuristics indicate this object is anomalous and carries a high-entropy payload, strongly suggesting exploitation of CVE-2018-0798. This technique is commonly used to execute arbitrary code. The embedded artifacts, including the OLE object and its native stream, are flagged as suspicious and likely contain the secondary payload.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/vKYPR4i2.zGgt 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` `2e6804a74f96b3e325133bdb8059f68214b52007477846abc8661f8a2c5b139f`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/vKYPR4i2.zGgt	2489856 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` `4f33d93c18e6f114cd90b47f86f64413e48eab46cbf5bb7e81bda651601022fb`	ole-package	OOXML xl/embeddings/vKYPR4i2.zGgt Ole10Native stream: ole10NAtiVE	2468281 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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