Malicious Office (OOXML) / .DOCX — malware analysis report

Heuristics 10

• Composite Moniker in RTF OLE object high CVE related RTF_COMPOSITE_MONIKER_RELATED
  (in altChunk RTF word/Astru.rtf) RTF contains Composite Moniker CLSID in OLE object context, but no nearby scriptlet/SCT payload was confirmed. Treat as related moniker attack-surface evidence rather than proof of CVE-2017-8570 exploitation.
• CVE-2026-21514 — Word/OLE security bypass in RTF high CVE likely CVE_2026_21514
  (in altChunk RTF word/Astru.rtf) RTF contains a hidden \svb hex package with DrsE2oDoc and downRevStg drawing compatibility parts. This matches an observed CVE-2026-21514 exploitation shape that manipulates Word's internal document structure and trust decisions.
• altChunk imports embedded RTF (RTF injection) critical OOXML_ALTCHUNK_RTF
  Document inlines an embedded RTF via an aFChunk relationship and a <w:altChunk> body element. This is the canonical RTF-injection wrapper used to smuggle RTF exploits (Equation Editor / URL Moniker / objdata) past DOCX-only scanners. Word opens the wrapper and executes the RTF inline. Recursing into the RTF for the exact exploit primitive.
• PE header (with DOS stub) in hex data critical RTF_MZ_HEX
  (in altChunk RTF word/Astru.rtf) Hex-encoded PE (MZ + DOS stub) found inside RTF — likely an embedded executable payload
• altChunk RTF auto-updates embedded executable object critical OOXML_ALTCHUNK_RTF_AUTOUPDATE_PE
  OOXML document imports an embedded RTF through altChunk; the RTF contains OLE object data, forces object update, and carries a hex-encoded PE payload. This is a stronger compound exploit-loader shape than a generic altChunk RTF wrapper, but it is not tied to a single CVE unless the nested RTF object primitive also matches one.
• \objupdate forces OLE activation high RTF_OBJUPDATE
  (in altChunk RTF word/Astru.rtf) RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
• Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
  (in altChunk RTF word/Astru.rtf) RTF contains ~1694KB of hex-encoded data inside \objdata sections — may hide a payload
• OLE object data medium RTF_OBJDATA
  (in altChunk RTF word/Astru.rtf) RTF contains 2 \objdata section(s) — embedded OLE objects
• Embedded OLE object medium RTF_OBJEMB
  (in altChunk RTF word/Astru.rtf) RTF contains \objemb — embedded OLE object
• Embedded URL info EMBEDDED_URL
  One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
  URL http://schemas.microsoft.com/office/word/2010/wordprocessingCanvas

  • http://schemas.microsoft.com/office/drawing/2014/chartex
  • http://schemas.openxmlformats.org/markup-compatibility/2006
  • http://schemas.openxmlformats.org/officeDocument/2006/relationships
  • http://schemas.openxmlformats.org/officeDocument/2006/math
  • http://schemas.microsoft.com/office/word/2010/wordprocessingDrawing
  • http://schemas.openxmlformats.org/drawingml/2006/wordprocessingDrawing
  • http://schemas.openxmlformats.org/wordprocessingml/2006/main
  • http://schemas.microsoft.com/office/word/2010/wordml
  • http://schemas.microsoft.com/office/word/2012/wordml
  • http://schemas.microsoft.com/office/word/2015/wordml/symex
  • http://schemas.microsoft.com/office/word/2010/wordprocessingGroup
  • http://schemas.microsoft.com/office/word/2010/wordprocessingInk
  • http://schemas.microsoft.com/office/word/2006/wordml
  • http://schemas.microsoft.com/office/word/2010/wordprocessingShape

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