Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 b9a2cc4768f7cb8f…

MALICIOUS

Office (OOXML) / .XLSX

2.90 MB Created: 2025-09-10 01:57:00 UTC Authoring application: Microsoft Excel 15.0300 First seen: 2026-02-05
MD5: 474cfd98f7e061ec5722e61cc3c9f494 SHA-1: ce987a18a4dea5f89f19bf1b80078c5ea6d56bfb SHA-256: b9a2cc4768f7cb8f0068cf385921f18c401e432309f4a0eb5cac867c792e1bd7
100 Risk Score

Malware Insights

MITRE ATT&CK
T1566.002 Spearphishing Attachment T1204.002 Malicious File

The sample is an Office Open XML spreadsheet containing an embedded OLE object, specifically identified as a Microsoft Equation Editor object. High-severity heuristics indicate that this Equation Editor object carries a payload-like Ole10Native stream with an anomalous header and size mismatch, strongly suggesting exploitation of a vulnerability within the Equation Editor component. This is a common delivery mechanism for malicious payloads.

Heuristics 3

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Embedded OLE object xl/embeddings/fm0.8bCW contains the Equation Editor CLSID, the legacy component exploited by CVE-2017-11882, CVE-2018-0802, and CVE-2018-0798.
  • 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

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
ooxml_oleobject_00.bin
ca7e554ed84a8aa9577b2919d2bc52b3290475e235b72c494cf23c86a202c909		 ooxml-ole-object OOXML embedded OLE part: xl/embeddings/fm0.8bCW 3004416 bytes
ooxml_oleobject_00_ole10native_00.bin
c75ecd1a0a3f31c20a0fbd03c106bd9a7768f843e8d16ce5bda1f2678a249467		 ole-package OOXML xl/embeddings/fm0.8bCW Ole10Native stream: ole10naTIvE 2978418 bytes

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