Malicious RTF — malware analysis report

Static analysis result for SHA-256 4108eee59c9e670d…

MALICIOUS

RTF

1.55 MB First seen: 2022-02-17
MD5: a4df636f2ccc799472fbf84404fdfd98 SHA-1: 1ca36144ab4fc8813e3e31844735f6fb01ec4249 SHA-256: 4108eee59c9e670d70fb06aaf6b366be919e6e6de298d6e198e7e16cefe06694
220 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File Execution: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1566.001 Phishing: Spearphishing Attachment

The RTF document contains an OLE object that exploits CVE-2017-11882, a known vulnerability in Microsoft Equation Editor. The presence of ".objupdate" and excessive hex data within the OLE object strongly suggests it's designed to embed and execute a secondary payload. The decoded OLE object's class is identified as EQUaTion.3, which is characteristic of this exploit. The document body is heavily obfuscated and does not provide direct clues to the payload's intent, but the exploit itself points to a downloader or dropper.

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 ~1620KB of hex-encoded data inside \objdata sections — may hide a payload
  • 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_off0000091f.bin
bbfdbb0dd17d7a45b94507bc3d2bc7232053c3be6cb3673c572c5695003b1790		 rtf-objdata-decoded RTF \objdata at offset 0x91F 810176 bytes

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