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

Static analysis result for SHA-256 f5755e4b677f1787…

MALICIOUS

Office (OLE) / .XLSX

228.9 KB
MD5: e5cd680b4c735672b135d6e7acb3cd02 SHA-1: 80664bb9311412d9f65a5ff08926479476081d36 SHA-256: f5755e4b677f1787f0403e22bc0c04de2c8e1674b6300e233e70facf7358f723
220 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 User Execution: Malicious File T1027 Obfuscated Files or Information T1203 Exploitation for Client Execution T1059 Command and Scripting Interpreter

The sample is a password-encrypted XLSX file that uses a default password to bypass detection. It contains an embedded OLE object (xl/embeddings/oleObject1.bin) that triggers CVE-2018-0798 in the Equation Editor, which is allowing for remote code execution via an anomalous OLe10NATivE stream with high entropy. The combination of encryption and a known exploit carrier shape is a common pattern for delivering second-stage payloads.

Heuristics 6

  • Equation Editor OLE object high CVE related OLE_EQUATION_EDITOR
    Default-encrypted OOXML embedded OLE object xl/embeddings/oleObject1.bin 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
    Default-encrypted OOXML contains embedded Equation Editor data with anomalous native stream bytes consistent with a CVE-2018-0798-style exploit. This is treated as likely CVE evidence because the Equation object is malformed and payload-like.
  • Encrypted Office package with CFB FAT corruption critical OLE_ENCRYPTED_AND_MALFORMED
    Encrypted-package shape co-occurs with FAT-chain corruption — the documented combined evasion form.
  • Default-encrypted OOXML exploit carrier layout high OOXML_ENCRYPTED_EXPLOIT_CARRIER_SHAPE
    Default-password encrypted OOXML package contains embedded OLE object parts and additional activation/decoy parts. This layout is common in malicious Excel exploit delivery and requires inspecting the decrypted package.
  • Office document is password-encrypted medium OFFICE_ENCRYPTED_PACKAGE
    OLE container holds MS-OFFCRYPTO encrypted package (Standard Encryption (Office 2007, AES)).
  • Office OOXML encrypted with default VelvetSweatshop password medium OFFICE_DEFAULT_PASSWORD_ENCRYPTED_OOXML
    OLE EncryptedPackage decrypts with Excel's built-in VelvetSweatshop password. Office opens this transparently, and malware uses it to hide OOXML exploit parts from scanners that only inspect the outer OLE container.

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