RTF / .DOC malware analysis — malicious · 9b45c66a2607e15d

MALICIOUS

RTF / .DOC

1.24 MB First seen: 2021-10-11

MD5: 8584e220963ef43c95c9f479263d6d28 SHA-1: 57e2abd01c1b911cac8e1a8c49b686605a6c14c5 SHA-256: 9b45c66a2607e15d8721ef5528dfec0573770cb89649a153ce8eda5ac5ed9a74

222 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF document contains an embedded OLE object that is indicative of the CVE-2017-11882 Equation Editor vulnerability. The presence of ".objupdate" and large amounts of hex-encoded data within the OLE object further support the exploitation of this vulnerability. The primary attack vector is likely spearphishing, with the embedded object designed to trigger arbitrary code execution upon opening.

Heuristics 6

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.
Split hex Equation Editor ProgID + OLE object critical 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.
\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 ~1297KB 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_off00001c43.bin` `835135df934edcf0d35f4703ea8026d80947af48eb1c5ae30e2989dcc75ad1a2`	rtf-objdata-decoded	RTF \objdata at offset 0x1C43	648637 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact entropy is 7.99, consistent with packed or encrypted content.

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