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

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 55,904 bytes but its declared streams total only 24,565 bytes — 31,339 bytes (56%) 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).

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