Malicious RTF — malware analysis report

Static analysis result for SHA-256 a4e6232abe167eff…

MALICIOUS

RTF

29.2 KB First seen: 2022-12-29
MD5: 6942cd86584a9b83c1d24e36c26dd688 SHA-1: 571a3ca512d35297fafa4888b4e25598b08fdb97 SHA-256: a4e6232abe167effc4237216190f9844d1f6ccc4778d3b2e2d59583d8c0dbf94
200 Risk Score

Malware Insights

MITRE ATT&CK
T1203 Exploitation for Client Execution

The sample is an RTF document that leverages the CVE-2017-11882 vulnerability in Microsoft Equation Editor. The presence of OLE object data and specific Equation Editor ProgIDs strongly indicates exploitation of this known vulnerability. This technique is commonly used to achieve arbitrary code execution, typically for downloading and running 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.
  • Automatically linked OLE object high RTF_OBJAUTLINK
    RTF contains \objautlink — an automatically linked OLE object surface that can be updated or activated when Word opens the document.
  • \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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off0000578d.bin
58c3e2c0d16494c9587cc73a13307811f95d218dcb2accfa7de37b6488361457		 rtf-objdata-decoded RTF \objdata at offset 0x578D 1648 bytes

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