Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 28af61aaa7d9e870…

MALICIOUS

RTF / .DOC

2.11 MB First seen: 2022-04-28
MD5: 552bec60e65293e406a2fd8e8e9af0d3 SHA-1: 82172748413f08aaad5f4261b0a9dc1040c2ad1c SHA-256: 28af61aaa7d9e87020bc614b762bb9bfda1371daaadb1de774eb5e1109d39574
180 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File

The RTF file contains multiple indicators of exploitation for CVE-2017-11882, specifically related to the Equation Editor (Equation.3). The presence of \objupdate and OLE object data strongly suggests that the embedded OLE object is designed to be activated, triggering the exploit. The decoded object data contains obfuscated JavaScript-like code, which likely facilitates the execution of a secondary payload. The attack pattern is consistent with a malicious document delivered via spearphishing, aiming to exploit a known vulnerability.

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.

FilenameKindSourceSize
objdata_00_off000012b8.bin
f6e3bd5cb9ccd7af8a17954e419870a2dc5732d0dc58c4a0f2a58f0f3741b1eb		 rtf-objdata-decoded RTF \objdata at offset 0x12B8 99814 bytes
objdata_01_off00045b27.bin
15b7f137c999929be510fea7aaa1c34a11c506a87bc2b1d42d45986f1d905f44		 rtf-objdata-decoded RTF \objdata at offset 0x45B27 457432 bytes

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