RTF malware analysis — malicious · 886c25a68d447e82

MALICIOUS

RTF

905.0 KB Authoring application: Riched20 6.3.9600 First seen: 2018-03-30

MD5: 3255b7646cd6cd0370ccf2719513517b SHA-1: 7eb5a8b653a0f00654be549a4f63ff7cbe9a8d13 SHA-256: 886c25a68d447e82b0e31e0dcaca4b09c9528a0aa206e40520f5dd77e227dd73

480 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of malicious activity, most critically the exploitation of CVE-2017-11882 through an embedded Equation Editor object. This vulnerability is known to be used for arbitrary code execution. The presence of PE headers in hex data and ClamAV detections for Agent and Dropper families further confirm its malicious nature, suggesting it acts as a dropper for further malicious payloads.

Heuristics 10

Equation Editor CLSID critical CVE likely RTF_EQUATION_EDITOR

Equation Editor OLE CLSID found inside an OLE object — exploited by CVE-2017-11882 / CVE-2018-0802 / CVE-2018-0798
CVE-2017-11882 — Equation Editor FONT record overflow critical CVE likely CVE_2017_11882

Equation Editor MTEF contains an overlong FONT typeface field, the vulnerable copy primitive for CVE-2017-11882. This is stronger evidence than the Equation Editor CLSID alone because it identifies the malformed record that drives code execution in EQNEDT32.EXE.
ClamAV: Win.Dropper.Remcos-9755127-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Win.Dropper.Remcos-9755127-0
PE header (with DOS stub) in hex data critical RTF_MZ_HEX

Hex-encoded PE (MZ + DOS stub) found inside RTF — likely an embedded executable payload
\objupdate forces OLE activation high RTF_OBJUPDATE

RTF contains \objupdate — forces automatic OLE object instantiation when the document is opened, bypassing user interaction. Almost exclusively seen in Equation Editor exploit documents.
Package object class high RTF_OBJCLASS_PACKAGE

OLE Package object — can wrap arbitrary files
Suspicious extracted artifact high EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
OLE object data medium RTF_OBJDATA

RTF contains 3 \objdata section(s) — embedded OLE objects
Embedded OLE object medium RTF_OBJEMB

RTF contains \objemb — embedded OLE object
OlePres presentation stream in RTF OLE object medium RTF_OLEPRES_STREAM

RTF contains an embedded OLE object with an OlePres presentation stream. OlePres is an OLE presentation marker and is not enough on its own to identify CVE-2025-21298.

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off000000ef.bin`	rtf-objdata-decoded	RTF \objdata at offset 0xEF	454896 bytes
SHA-256: `65091c7c5dce7197f33898663795b3deb9a9b1de741079a016df1a6b5daeed56`
Detection ClamAV: Win.Dropper.Remcos-9755127-0 Obfuscation or payload: unlikely
`objdata_01_off000de31e.bin`	rtf-objdata-decoded	RTF \objdata at offset 0xDE31E	3980 bytes
SHA-256: `885a022b4bc453723d3c8f22f635e1c3d6f514572c2f1ecb9bb06ee0333cad0f`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered command string(s): cmd.exe /c%tmp%\preview.exe &��D$,f-Q��%
`objdata_02_off000e0564.bin`	rtf-objdata-decoded	RTF \objdata at offset 0xE0564	3546 bytes
SHA-256: `5a90c8a6b982fcc963e17f4ae5d4e4578082efed34172016978554f1014b7ff8`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered command string(s): cmd.exe /c%tmp%\preview.exe AC

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