Malicious RTF / .DOC — malware analysis report

Static analysis result for SHA-256 a096578d9c00b1a5…

MALICIOUS

RTF / .DOC

1.69 MB First seen: 2022-03-24
MD5: 5c32b3d822639887c4f895da2a219522 SHA-1: a04e7c6585b0bcf65153f4f70679a7e835d825a1 SHA-256: a096578d9c00b1a506bbb455a419434e3ce909b87fa7bc314d8a06648eb434ac
220 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File Execution: Malicious File T1566.001 Phishing: Spearphishing Attachment

The sample is an RTF document containing an embedded OLE object that leverages the Equation Editor vulnerability (CVE-2017-11882). The heuristic firings indicate the presence of OLE object data, an Equation Editor ProgID, and an ".objupdate" directive, all pointing to exploitation of this known vulnerability. The decoded OLE object is substantial in size and exhibits high entropy, suggesting it likely contains a second-stage payload. The document body is heavily obfuscated and does not provide clear user-facing content, reinforcing the interpretation that its primary purpose is exploitation.

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 ~1762KB 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_off00001179.bin
f61bf681e8416fc465585d7619f3a699a47066d5bb7f26137159ef327f2b8207		 rtf-objdata-decoded RTF \objdata at offset 0x1179 881255 bytes

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