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

Static analysis result for SHA-256 12fbde27c15a5c8d…

MALICIOUS

Office (OLE) / .XLS

107.5 KB Created: 1996-12-17 01:32:42 Authoring application: Microsoft Excel
MD5: 3b8f316eddd557d2febf516079e07bb0 SHA-1: ce0d663474e54eb5459321cb1ee1e90c03a20b79 SHA-256: 12fbde27c15a5c8db8e8e4e474128528d4b69a0862bb14a3c25f80d017871375
140 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution

The critical heuristic firing indicates the sample exploits CVE-2009-3129, a known vulnerability in Microsoft Excel. This vulnerability allows for the execution of arbitrary code, likely to download and run a secondary payload. The large slack space in the OLE structure is also indicative of a packed or obfuscated malicious payload.

Heuristics 3

  • 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.
  • Reference to CreateProcess API high SC_STR_CREATEPROCESS
    Reference to CreateProcess API
  • OLE document has large unaccounted-for region high OLE_SLACK_ANOMALY
    OLE file is 110,080 bytes but its declared streams total only 24,565 bytes — 85,515 bytes (78%) 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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