RTF malware analysis — malicious · 98af6635138045ca

MALICIOUS

RTF

1.73 MB Authoring application: Riched20 10.0.14393 First seen: 2020-09-07

MD5: 7e461f6366681c5ae24920a31c3cfec6 SHA-1: 3513d238a659d27f1ff3acea55e84fafa093c676 SHA-256: 98af6635138045cae3f29995a587d0c8a7f14446a9d10564677dd4a41372c3f1

240 Risk Score

Malware Insights

MITRE ATT&CK

T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of exploitation targeting CVE-2017-11882, a known vulnerability in Microsoft Equation Editor. The presence of OLE objects, specifically related to Equation Editor, and the ".objupdate" directive strongly suggest an attempt to trigger code execution. The large amount of hex-encoded data within the OLE objects likely hides a malicious payload, which is then executed via the exploitation of this vulnerability.

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 activation — CVE-2017-11882 related high CVE related CVE_2017_11882_ACTIVATION_RELATED

RTF decodes to an Equation.3 ProgID and requests OLE activation with \objemb plus \objupdate. This reaches the legacy Equation Editor attack surface used by CVE-2017-11882/CVE-2018-0802 documents, but the malformed MTEF/native payload needed for stronger attribution was not recovered.
\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 ~1001KB of hex-encoded data inside \objdata sections — may hide a payload
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
Suspicious extracted artifact medium 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 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off00117a70.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x117A70	331171 bytes
SHA-256: `b0fc54d4cadd26c142356cda98a09805637bba7ef7a4cd1336fd6bbe4507d112`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis found candidate code region(s). Indicators: heap spray 0x41 (A) Carved artifact contains 1 shell/COM execution token(s).
`objdata_01_off001b95de.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x1B95DE	1709 bytes
SHA-256: `6ef048de06e9c2e6b420e78a489e52123766b08549a074a5f95b98ffe8558f38`
Detection ClamAV: No threats found Obfuscation or payload: likely Static shellcode analysis found candidate code region(s). Indicators: SC_PEB_ACCESS
`objdata_02_off001b95ee.bin`	rtf-objdata-decoded	RTF \objdata at offset 0x1B95EE	36 bytes
SHA-256: `8935eb605040753f89379b3f05c2cdaefba833ec64299ed9c258020f4c1217b0`

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