RTF malware analysis — malicious · ac64adbfa128fd5f

MALICIOUS

RTF

1.60 MB First seen: 2022-05-09

MD5: 696a2aa5504dd974e6610592e69ba789 SHA-1: 9d9e4c1fff54da830a54d6e915cfc083b147f87f SHA-256: ac64adbfa128fd5f31bd922957942a1b80c56ee119791a29b939be04e1d7e2ba

180 Risk Score

Malware Insights

MITRE ATT&CK

T1566.001 Spearphishing Attachment T1204.002 Malicious File

The RTF document contains an embedded OLE object specifically targeting the Equation Editor vulnerability (CVE-2017-11882). The presence of `RTF_EQUATION_EDITOR` and `CVE_2017_11882_ACTIVATION_RELATED` heuristics strongly indicates exploitation of this known vulnerability. The `RTF_OBJUPDATE` heuristic suggests that the OLE object is automatically activated upon opening the document, leading to the execution of the embedded payload. The decoded object data, although truncated, contains VBA-like code that appears to be part of a larger malicious script, likely responsible for downloading and executing a second-stage payload.

Heuristics 5

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.
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.
OLE object data medium RTF_OBJDATA

RTF contains 2 \objdata section(s) — embedded OLE objects
Embedded OLE object medium RTF_OBJEMB

RTF contains \objemb — embedded OLE object

Extracted artifacts 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`objdata_00_off000012ab.bin` `6621d0690a361955188be31528ad7b59c27d476836a43d1c42fe2da91873f3e9`	rtf-objdata-decoded	RTF \objdata at offset 0x12AB	86808 bytes
`objdata_01_off0003724a.bin` `c6836530895d3068b0bd13b6673e20cfb3c2472da47cd4c3fb2419898144731b`	rtf-objdata-decoded	RTF \objdata at offset 0x3724A	345132 bytes

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