Win.Malware.Remcos-6960008-0 RTF malware analysis — malicious · 1edadef7e2309bc3

MALICIOUS

RTF

1.24 MB Authoring application: Riched20 6.3.9600 First seen: 2019-04-18

MD5: ebfd40c40529587c10e5b4e15dfaa84f SHA-1: 14a8ace7c1d53a4d666f7ba8f11cc247682e34a1 SHA-256: 1edadef7e2309bc32fc2b9c7412c3ecf712e773b0812a12d9a2d2b21e7413b1b

520 Risk Score

Malware Insights

Win.Malware.Remcos-6960008-0 · confidence 95%

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains embedded OLE objects, specifically exploiting the Equation Editor vulnerability CVE-2017-11882. This vulnerability is known to be used for client-side execution of arbitrary code. The ClamAV detection of Win.Malware.Remcos-6960008-0 on the main file and extracted artifacts strongly suggests this family. The presence of PE headers within hex-encoded data further indicates a packed or embedded executable payload.

Heuristics 11

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.Malware.Remcos-6960008-0 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Win.Malware.Remcos-6960008-0
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
Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX

RTF contains ~1278KB of hex-encoded data inside \objdata sections — may hide a payload
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	639189 bytes
SHA-256: `3001fcbd04a13c2fc9fc8b2ae8362068f8c5e8ae52a414a80988b82e99f7c0e6`
Detection ClamAV: Win.Malware.Remcos-6960008-0 Obfuscation or payload: unlikely
`objdata_01_off001382e8.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x1382E8	3980 bytes
SHA-256: `c1b39ce5ca35d49fb40c33940ae77a4445ecb6769893147b9fa594bfc9e68cdf`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered command string(s): cmd.exe /c%tmp%\word.exe &��D$,f-Q��%
`objdata_02_off0013a52e.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x13A52E	3546 bytes
SHA-256: `5c1f169557fef3c4b9920b337bc5e1b4ff7c0fec472e5e8c46b7962417cddca9`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered command string(s): cmd.exe /c%tmp%\word.exe AC

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