Malicious RTF — malware analysis report

Static analysis result for SHA-256 5f397327aeb20718…

MALICIOUS

RTF

5.4 KB First seen: 2026-02-03
MD5: 8b8903b0e7b7a1a7f501277624bc7e6b SHA-1: 858e841b91f16d3567b133b3c90d01e0499d5169 SHA-256: 5f397327aeb20718e364bef61e8bad507772708a7d1bf55d8b845170c69f3de0
220 Risk Score

Malware Insights

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

The RTF file contains an embedded OLE object with a CLSID pointing to Shell.Explorer.1, which is indicative of an exploit targeting CVE-2026-21509. This vulnerability allows for arbitrary code execution when the OLE object is activated, likely through the ".objupdate" directive. The file is classified as malicious due to this exploit, and the IOCs highlight the specific components involved in the attack.

Heuristics 5

  • CVE-2026-21509 — Shell.Explorer.1 CLSID in RTF critical CVE related CVE_2026_21509
    RTF document contains the Shell.Explorer.1 CLSID {EAB22AC3-30C1-11CF-A7EB-0000C05BAE0B} associated with CVE-2026-21509 (OLE/COM Killbit / Protected View bypass). Actively exploited in the wild.
  • ClamAV: Rtf.Exploit.CVE_2026_21509-10059214-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Rtf.Exploit.CVE_2026_21509-10059214-0
  • 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_off00000107.bin
b8a6f8b14d9d6952dd9beb18ffca73f9b9c1d46e62ba26242c05d7fa06fbb985
rtf-objdata-decoded RTF \objdata at offset 0x107 2609 bytes