RTF malware analysis — malicious · 8c18cdfebc67d394

MALICIOUS

RTF

521.0 KB Authoring application: Riched20 6.3.9600 First seen: 2019-03-10

MD5: c432a102616f69d0526a5935a1378407 SHA-1: 1cf7db507591f7fb60479475f7ca7a828c1272d4 SHA-256: 8c18cdfebc67d39405dd574c393ab92d1ea1a616bc15524aa6536410ad15275f

420 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The sample is an RTF document containing embedded OLE objects, specifically triggering the CVE-2017-11882 vulnerability in Equation Editor. This exploit allows for the execution of arbitrary code, likely to download and run a secondary payload. The presence of PE headers in hex data and suspicious extracted artifacts further supports this conclusion.

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: Rtf.Exploit.CVE_2017_11882-6584355-1 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Rtf.Exploit.CVE_2017_11882-6584355-1
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	258288 bytes
SHA-256: `c87d3d76ea41ef11d6425d1d91da179fa3a06a502bdc0cd5359a71139eab3cf0`
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.88, consistent with packed or encrypted content.
`objdata_01_off0007e31e.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x7E31E	3980 bytes
SHA-256: `48e76013cfeda5e9a94f082e775a5cb6b54c98d7529d5d28c472b7f6eef3d4e3`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered command string(s): cmd.exe /c%tmp%\Windows.exe &��D$,f-Q��%
`objdata_02_off00080564.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x80564	3546 bytes
SHA-256: `255e86b121e583046ff506f12b61d2353ac7432188993e8631fee626ca764ed5`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis recovered command string(s): cmd.exe /c%tmp%\Windows.exe AC

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