Office (OOXML) / .XLSX malware analysis — malicious · a6c5753c81ce3ebb

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 3829ed80f6dd5b899d1e020047a80020 SHA-1: 55bdfdc27ca7c48d9d2fae9a93a5709e7620ee6d SHA-256: a6c5753c81ce3ebb530a67efd2e2650ba48e4151af6e864c96dbbd20caa5b1c7

142 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1204.001 Malicious Link

The sample is an Office Open XML (OOXML) XLSX file containing an embedded OLE object, specifically identified as a Microsoft Equation Editor object. High-severity heuristics indicate that this Equation Editor object is anomalous and carries a payload-like Ole10Native stream, strongly suggesting exploitation of CVE-2018-0798. This technique is commonly used to deliver a second-stage malicious payload. No VBA macros or scripts were extracted, but the presence of the vulnerable OLE object is sufficient evidence of the attack vector.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/sG.F91A70 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` `ff47815c133f14ec3f1e4853fbb5d368a59f47414b6041f7a6e4ba301a9726ae`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/sG.F91A70	2566144 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` `7a59fa268585758eb7d8d2f071db0fb23ee4a671dfb6cd524f85adf31bb7b04a`	ole-package	OOXML xl/embeddings/sG.F91A70 Ole10Native stream: Ole10Native	2543496 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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