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

Static analysis result for SHA-256 81dbb9a460eb8e65…

MALICIOUS

Office (OLE) / .XLS

66.0 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel First seen: 2026-05-11
MD5: f815254d205d7ee73f8cf4a2004c023e SHA-1: 8722738356f999b826ed8811ef86db6affd146bc SHA-256: 81dbb9a460eb8e652ef1846816607e8e9c9c5cb43ab1c7e8cf81e6320b4b4095
100 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution

The file is a Microsoft Excel spreadsheet that triggers a critical heuristic for CVE-2009-3129, indicating an exploitation for client execution. The large slack space in the OLE document also suggests potential obfuscation or embedded malicious content. No specific family could be identified.

Heuristics 2

  • CVE-2009-3129 — Excel FEATHEADER record overflow critical CVE exact CVE_2009_3129
    Workbook BIFF stream contains a FEATHEADER (Feature Header) record with anomalous size (record_size=23, isf=2, cbHdrData=4294967295). Legitimate FEATHEADER records are tiny (<100 bytes) and carry cbHdrData values that fit in the record body; the value here is the documented CVE-2009-3129 exploit primitive — cbHdrData drives a memcpy with attacker-controlled size, leading to memory corruption and code execution in Excel 2007/2003.
  • OLE document has large unaccounted-for region high OLE_SLACK_ANOMALY
    OLE file is 67,584 bytes but its declared streams total only 24,565 bytes — 43,019 bytes (64%) live in unallocated sector slack. This is the canonical hiding place for pre-macro-era Office exploit payloads (XOR-encoded shellcode reached via a parser pointer-corruption bug in the document structure).