Malicious RTF — malware analysis report

Static analysis result for SHA-256 a5bb2090a9c4eff2…

MALICIOUS

RTF

887.8 KB First seen: 2020-05-25
MD5: 43e468b912b68f2fdb61588f85533239 SHA-1: 7212c22e42d58e93e7849b079feb846fd444fd3d SHA-256: a5bb2090a9c4eff21435b06c4a2911cd53db69af484a3d13f035f3e9c13f0949
180 Risk Score

Malware Insights

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

The RTF file contains an embedded OLE object that triggers CVE-2017-11882, a known vulnerability in Microsoft Equation Editor. This vulnerability allows for the execution of arbitrary code upon activation, likely leading to the download and execution of a second-stage payload. The file's malicious nature is confirmed by the critical heuristic firing related to Equation Editor exploitation.

Heuristics 5

  • Obfuscated Equation Editor ProgID + activation critical CVE related RTF_EQUATION_EDITOR
    RTF decodes to an Equation.3 ProgID from top-level \objdata hex after nested RTF junk groups are ignored, and the document also contains \objemb plus \objupdate activation. This is an obfuscated Equation Editor exploit surface associated with CVE-2017-11882 / CVE-2018-0802 families, but no exact malformed MTEF CVE primitive was recovered from this object.
  • 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.
  • OLE object data medium RTF_OBJDATA
    RTF contains 1 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00000a2e.bin rtf-objdata-decoded RTF \objdata at offset 0xA2E 100610 bytes
SHA-256: bbd6c56af772db31e9d3b360480ece08b5775ccf559adecf0ff2c5be0d109fe1

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