Office (OOXML) / .XLSX malware analysis — malicious · 979d192986ba2c96

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: ecbb1e8f1edfae9e395dd70dec621ce2 SHA-1: 8b45b3856282bbd01b30a1900cf03a942edefdbb SHA-256: 979d192986ba2c9632c37412fdce0ddec349cadfed15cea2175cec1b285f19e8

142 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1027 Obfuscated Files or Information

The sample is an XLSX file containing an embedded OLE object with a high-entropy Ole10Native stream. This is indicative of a CVE-2018-0798 vulnerability exploitation attempt, as signaled by the high-entropy payload in the Equation Editor object (xl/embeddings/NryAM8.F9v). No scripts were extracted from this sample, but the high entropy of the carved artifacts (ooxml_oleobject_00_ole10native_00.bin) suggests an encrypted or compressed second-stage payload.

Heuristics 5

Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR

Embedded OLE object xl/embeddings/NryAM8.F9v 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` `9313b2b5fbcd18d23f4b9d620e8cdbe7532b6144cf0eac0f23eb03ea23a9d647`	ooxml-ole-object	OOXML embedded OLE part: xl/embeddings/NryAM8.F9v	2216448 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` `de48fcfe97358915dc197b96bd97dd0ec31bdc0e8d4b5fd9637d3510168d2db9`	ole-package	OOXML xl/embeddings/NryAM8.F9v Ole10Native stream: Ole10Native	2196863 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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