Malicious RTF — malware analysis report

Static analysis result for SHA-256 604f8b6cb27fc3e8…

MALICIOUS

RTF

1.79 MB First seen: 2022-05-26
MD5: 79b069c9ad93309ee526ce5fa70e535e SHA-1: c04be61d6e0971cb8543d7dc0930f613252adc72 SHA-256: 604f8b6cb27fc3e83849c6afa3bc2736ef58dc7f00ec4d9eaf3834321d251572
220 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The RTF file contains multiple indicators of exploitation for CVE-2017-11882, including OLE object data and a specific ProgID related to Equation Editor. The presence of a large, hex-encoded OLE object suggests it is hiding a payload. The RTF_OBJUPDATE heuristic indicates that the OLE object is designed to be activated automatically, leading to the execution of the embedded exploit.

Heuristics 5

  • 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 ~1873KB 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00001b3b.bin
9a627a20812013653a85becae8ed86caabef52af72529751f68d21903608e678		 rtf-objdata-decoded RTF \objdata at offset 0x1B3B 936703 bytes

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