Malicious PDF — malware analysis report

Static analysis result for SHA-256 15fe5637bdf8efcc…

MALICIOUS

PDF

8.95 MB First seen: 2021-05-26
MD5: daeb4233ee2dbff33c0c321b587aa443 SHA-1: 2e8c61321f46e55eeaf8da926140b778a5046093 SHA-256: 15fe5637bdf8efcc70e3760798caf2b0e0bcec1bdac26ef1f21a5c68937911b7
460 Risk Score

Malware Insights

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

The sample is identified as malicious due to multiple critical heuristic firings indicating exploitation of CVE-2017-11882 and CVE-2017-8759 through embedded OLE objects, specifically the Equation Editor. The presence of shellcode command strings within an extracted artifact further supports the execution of a malicious payload. The document body content is nonsensical and likely obfuscated or corrupted.

Machine Learning

  • Nyx PDF Classifier clean score 0.0148

Heuristics 10

  • Equation Editor CLSID critical CVE likely RTF_EQUATION_EDITOR
    Equation Editor OLE CLSID found inside an OLE object — exploited by CVE-2017-11882 / CVE-2018-0802 / CVE-2018-0798
  • CVE-2017-11882 — Equation Editor FONT record overflow critical CVE likely CVE_2017_11882
    Equation Editor MTEF contains an overlong FONT typeface field, the vulnerable copy primitive for CVE-2017-11882. This is stronger evidence than the Equation Editor CLSID alone because it identifies the malformed record that drives code execution in EQNEDT32.EXE.
  • CVE-2017-8759 — MSXML SAX OLE activation critical CVE likely CVE_2017_8759
    RTF contains a hex-encoded OLE1 object for Msxml2.SAXXMLReader.6.0 followed by an embedded OLE compound document, and the document requests OLE activation. This matches the RTF staging shape used for CVE-2017-8759 SOAP/WSDL parser code injection.
  • ClamAV: Rtf.Exploit.CVE_2017_11882-6398227-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Exploit.CVE_2017_11882-6398227-0
  • Equation Editor object class critical RTF_OBJCLASS_EQUATION
    Object class 'equation.3' references Equation Editor
  • \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 ~9337KB of hex-encoded data inside \objdata sections — may hide a payload
  • Suspicious extracted artifact high EXTRACTED_FILE_STATIC_TRIAGE
    One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.
  • 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_off00000cec.bin rtf-objdata-decoded RTF \objdata at offset 0xCEC 3546 bytes
SHA-256: b772fd19f3b2eac93243486f88405e6df31d894382210b228ec780d3751277ef
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Static shellcode analysis recovered command string(s): cmd.exe /c calc.exe &AAAAAAAAAAAAAAAAAAAAAAA C

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