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

Static analysis result for SHA-256 ff4f37dc769eec39…

MALICIOUS

Office (OLE) / .XLS

153.5 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel
MD5: 6ff164d20870b98f318da9b7792ba40f SHA-1: ab739903ff6ab7c05df0ad9039dfd69d6b175b8a SHA-256: ff4f37dc769eec3900ccc13ef681c5b1a0fa0c64648e33b1ec78c3b3016a41d1
100 Risk Score

Malware Insights

MITRE ATT&CK
T1204 Malicious Link T1204.002 Malicious Link: Malicious File

The sample is an Excel file identified as malicious due to a critical heuristic firing for CVE-2009-3129, a known vulnerability in Microsoft Excel's FEATHEADER record. This exploit likely allows for arbitrary code execution, enabling the delivery of a secondary payload. The large slack space in the OLE structure is also anomalous and may be used to hide malicious content.

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=22, isf=4, cbHdrData=4). 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 157,208 bytes but its declared streams total only 24,565 bytes — 132,643 bytes (84%) 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).