Malware Insights
The sample is a malicious OOXML document that leverages an altChunk to import an RTF object. This RTF object contains embedded OLE objects and exhibits excessive hex data, including a PE header. The critical heuristic 'OOXML_ALTCHUNK_RTF_AUTOUPDATE_PE' indicates that the altChunk RTF auto-updates an embedded executable. The 'CVE_2026_21514' heuristic specifically points to a Word/OLE security bypass vulnerability being exploited. The external relationship to 'Student report with photo.dotx' suggests a potential lure or template. The primary attack vector involves exploiting a known vulnerability to execute an embedded payload.
Heuristics 11
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Composite Moniker in RTF OLE object high RTF_COMPOSITE_MONIKER_RELATED(in altChunk RTF word/Elerat.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.
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CVE-2026-21514 — Word/OLE security bypass in RTF high CVE likely CVE_2026_21514(in altChunk RTF word/Elerat.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.
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altChunk imports embedded RTF (RTF injection) critical OOXML_ALTCHUNK_RTFDocument 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.
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PE header (with DOS stub) in hex data critical RTF_MZ_HEX(in altChunk RTF word/Elerat.rtf) Hex-encoded PE (MZ + DOS stub) found inside RTF — likely an embedded executable payload
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altChunk RTF auto-updates embedded executable object critical OOXML_ALTCHUNK_RTF_AUTOUPDATE_PEOOXML 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.
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\objupdate forces OLE activation high RTF_OBJUPDATE(in altChunk RTF word/Elerat.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.
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Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX(in altChunk RTF word/Elerat.rtf) RTF contains ~2275KB of hex-encoded data inside \objdata sections — may hide a payload
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External relationship high OOXML_EXTERNAL_RELExternal target in word/_rels/settings.xml.rels: file:///C:\Users\John\AppData\Roaming\Microsoft\Templates\Student report with photo.dotx
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OLE object data medium RTF_OBJDATA(in altChunk RTF word/Elerat.rtf) RTF contains 2 \objdata section(s) — embedded OLE objects
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Embedded OLE object medium RTF_OBJEMB(in altChunk RTF word/Elerat.rtf) RTF contains \objemb — embedded OLE object
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Embedded URL info EMBEDDED_URLOne 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
Extracted artifacts 3
Files carved from inside the sample during analysis.
| Filename | Kind | Source | Size |
|---|---|---|---|
objdata_00_off000af73f.binaecf2f4802454c3e7406bbca74f152ad4889288d299c262f41df3b68df08c227 |
rtf-objdata-decoded | RTF \objdata at offset 0xAF73F | 1033882 bytes |
objdata_01_off002b3bcf.bin24ee741dd41bc27803d80f81b66eba686fe8f5d17bd847727dc5d94834bd3188 |
rtf-objdata-decoded | RTF \objdata at offset 0x2B3BCF | 584826 bytes |
rtf_svb_00000009.zip2352c9fffd0fd8eba341b4fd80ae0a94a85929bec042e2061b1f17cd52df50f2 |
rtf-svb-package | RTF \svb hex-decoded ZIP at offset 0x9 | 116884 bytes |
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