Malicious RTF — malware analysis report

Static analysis result for SHA-256 772fb7ffce47f8e8…

MALICIOUS

RTF

1.39 MB First seen: 2021-06-17
MD5: 1c5079cc5866d9deec2cccf078521ed0 SHA-1: a1a166d0564a5c239470c558ec6f65e7a3627cc6 SHA-256: 772fb7ffce47f8e8cc4df8d1807165f16569ec7491d119c32a2c1dc1ff685ab0
180 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, specifically related to the Equation Editor. The presence of OLE objects and the explicit firing of heuristics for Equation Editor and OLE activation strongly suggest this vulnerability is being leveraged. The embedded data, while obfuscated, likely contains a payload designed to be executed by the exploit, leading to arbitrary code execution.

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_off000011e1.bin rtf-objdata-decoded RTF \objdata at offset 0x11E1 53277 bytes
SHA-256: 842bcac84c9672a0340a1ba19797e72d5a4796a84324d051551459dc9853e627
objdata_01_off0002ec8b.bin rtf-objdata-decoded RTF \objdata at offset 0x2EC8B 346025 bytes
SHA-256: 5d913e0bdd4543b59117490fda1dba3c38edbcd2b81c5376d07402a696f7c2ab

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