Win.Dropper.Nanocore-9893680-0 — RTF malware analysis

Static analysis result for SHA-256 110143b38ce2a1ea…

MALICIOUS

RTF

2.74 MB Created: 2018-05-21 15:22:00 First seen: 2020-02-04
MD5: 6b97b5868969bdbeadf6fc15fb169f50 SHA-1: 7d308736bdb42f2caa2749f64397169673cdd83a SHA-256: 110143b38ce2a1ea344f86363ba56ce571e38e58f01d84caeb6687ecaef60c26
502 Risk Score

Malware Insights

Win.Dropper.Nanocore-9893680-0 · confidence 95%

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

The RTF document contains embedded OLE objects, specifically exploiting CVE-2017-8759 through MSXML SAX OLE activation. This technique is commonly used to deliver secondary payloads, as indicated by the ClamAV detection of Win.Dropper.Nanocore-9893680-0 and the presence of a suspicious extracted artifact named objdata_01_off00299061.bin. The excessive hex data within OLE objects further suggests the hiding of malicious code.

Heuristics 12

  • 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-2017-8759 — 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.
  • Ole10Native stream in RTF OLE object high CVE related RTF_OLE10NATIVE_STREAM
    RTF contains an embedded OLE object with an Ole10Native stream. This is a strong payload-container signal and is related to Word/OLE exploit delivery, but it is not specific enough on its own to assign a CVE.
  • ClamAV: Win.Dropper.Nanocore-9893680-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Dropper.Nanocore-9893680-0
  • \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.
  • Package object class high RTF_OBJCLASS_PACKAGE
    OLE Package object — can wrap arbitrary files
  • Large hex data blocks in OLE object high RTF_EXCESSIVE_HEX
    RTF contains ~2603KB 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 2 \objdata section(s) — embedded OLE objects
  • Embedded OLE object medium RTF_OBJEMB
    RTF contains \objemb — embedded OLE object
  • OlePres presentation stream in RTF OLE object medium RTF_OLEPRES_STREAM
    RTF contains an embedded OLE object with an OlePres presentation stream. OlePres is an OLE presentation marker and is not enough on its own to identify CVE-2025-21298.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://ocsp.thawte.com0 In RTF body
    • http://ts-ocsp.ws.symantec.com07In RTF body
    • http://schemas.microsoft.comIn RTF body
    • http://crl.thawte.com/ThawteTimestampingCA.crl0In RTF body
    • http://ts-aia.ws.symantec.com/tss-ca-g2.cer0In RTF body
    • http://ts-crl.ws.symantec.com/tss-ca-g2.crl0(In RTF body

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off00002a8a.bin rtf-objdata-decoded RTF \objdata at offset 0x2A8A 1301505 bytes
SHA-256: 24d9cad002ccbc393045c87854b2a49d374f432cfaab8ef429d36a6993df2602
Detection
ClamAV: Win.Dropper.Nanocore-9893680-0
Obfuscation or payload: unlikely
objdata_01_off00299061.bin rtf-objdata-decoded RTF \objdata at offset 0x299061 23598 bytes
SHA-256: 9d6812245bb9a9acb8a063c32175f2d2d79fdda37feb88384d730b4323f75b05
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Static shellcode analysis found candidate code region(s). Indicators: SC_PEB_ACCESS Static shellcode analysis recovered command string(s): cmd.exe /c %tmp%\A.X %

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