Office (OOXML) / .DOCX malware analysis — malicious · 5875835796f05ac1

MALICIOUS

Office (OOXML) / .DOCX

322.6 KB Created: 2016-07-28 11:04:00 UTC Authoring application: Microsoft Office Word 16.0000

MD5: 6976a6c4d2a219e23650c359ed1c87a5 SHA-1: 9b1ab8d630269546a3ea830d5a5793a1bd745583 SHA-256: 5875835796f05ac1960444de9c4eda1e08e4eafbc668b7aa71e3a51a73576130

180 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1204.002 Malicious File

The sample is a malicious OOXML document that leverages the altChunk mechanism to import an embedded RTF file. This RTF file contains OLE objects and is configured to trigger an update via \objupdate, exploiting CVE-2026-21514. This indicates the document is designed to bypass security controls and execute embedded malicious content, likely a second-stage payload.

Heuristics 6

CVE-2026-21514 — Word/OLE security bypass in RTF high CVE likely CVE_2026_21514

(in altChunk RTF word/el.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.
\objupdate forces OLE activation high RTF_OBJUPDATE

(in altChunk RTF word/el.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.
OLE object data medium RTF_OBJDATA

(in altChunk RTF word/el.rtf) RTF contains 2 \objdata section(s) — embedded OLE objects
Embedded OLE object medium RTF_OBJEMB

(in altChunk RTF word/el.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

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off000af79f.bin` `70680439422a115970299513c9a15844d3d99cf2ee2fda001d14dce3f78515eb`	rtf-objdata-decoded	RTF \objdata at offset 0xAF79F	78401 bytes
`objdata_01_off000e0b9e.bin` `7cedd8bade393af92a8beca2e2e4157dcb12a631247d0587ca24215aea88ac22`	rtf-objdata-decoded	RTF \objdata at offset 0xE0B9E	584266 bytes
`rtf_svb_00000009.zip` `28fc295dafc0bcccd998d6dc34a4e9ae47eb34cb74cb4b892eb6454833467799`	rtf-svb-package	RTF \svb hex-decoded ZIP at offset 0x9	116932 bytes

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