RTF malware analysis — malicious · 071a443f90801970

MALICIOUS

RTF

5.15 MB First seen: 2021-06-13

MD5: 591a77f7f1c582bd2c6771a1d58dcac4 SHA-1: e5e1e834432fcd848dbb86eed0c412e82259348a SHA-256: 071a443f908019703f0192a69cfbdfc74945e7ebbe46b0808d15f696a9cf1b54

262 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF document contains OLE object data, specifically related to Equation Editor, which strongly indicates the exploitation of CVE-2017-11882. This vulnerability allows for the execution of arbitrary code, likely to download and run a second-stage payload. The presence of a large, high-entropy OLE1 native payload further supports this conclusion.

Heuristics 7

Split hex Equation Editor ProgID + OLE object critical CVE likely RTF_EQUATION_EDITOR

RTF embeds the Equation.3 ProgID as hex bytes near OLE object activation and splits the byte stream with whitespace or an ignorable RTF group. This is an Equation Editor OLE activation surface commonly used by CVE-2017-11882 / CVE-2018-0802 exploit documents.
Equation Editor OLE1 native payload — CVE-2017-11882 related critical CVE related CVE_2017_11882_RELATED

RTF decodes to an OLE1 Equation.3 embedded object whose native data is large and payload-like, and \objupdate requests automatic activation. This is the delivery shape used by Equation Editor RCE documents such as CVE-2017-11882/CVE-2018-0802, but the malformed MTEF record needed for exact attribution was not recovered.
Automatically linked OLE object high RTF_OBJAUTLINK

RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
\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.
Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX

RTF contains ~5400KB of hex-encoded data inside \objdata sections — may hide a payload
OLE object data medium RTF_OBJDATA

RTF contains 2 \objdata section(s) — embedded OLE objects
Suspicious extracted artifact info 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off000000ac.bin`	rtf-objdata-decoded	RTF \objdata at offset 0xAC	2700411 bytes
SHA-256: `caaa3746a53dbbfbada4e82d7f6244c9c9374e29cd1cef059a48b6474c87f516`
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 8.00, consistent with packed or encrypted content.

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