Malicious RTF — malware analysis report

Static analysis result for SHA-256 bcd5a29dc0100661…

MALICIOUS

RTF

1.24 MB First seen: 2023-05-18
MD5: 8bb2f3900a79c896bc1098b6131891ed SHA-1: 853ecd3d0b55ef1a08a4bfcc9373cfebbf910257 SHA-256: bcd5a29dc0100661ff60afd0811f47c0243f16bef13ce4602cf844f65404257e
222 Risk Score

Malware Insights

MITRE ATT&CK
T1566.001 Spearphishing Attachment T1204.002 Malicious File T1059.003 Windows Command Shell

The RTF file contains an OLE object with decoded data that matches the characteristics of the CVE-2017-11882 Equation Editor vulnerability. This vulnerability is known to be used to embed and execute arbitrary code, typically a PE file, which is consistent with the high entropy and MZ offset found in the decoded object. The file likely serves as a dropper for a secondary malicious payload.

Heuristics 6

  • 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.
  • Decoded Equation Editor payload + PE critical RTF_EQUATION_EDITOR
    RTF decodes to an Equation Editor ProgID adjacent to OLE activation and the same decoded object stream contains embedded PE bytes. This matches the Equation Editor exploit surface used by CVE-2017-11882 / CVE-2018-0802 documents, while requiring payload evidence to avoid flagging benign Equation references.
  • \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 ~1300KB 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
  • Suspicious extracted artifact info 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
objdata_00_off0000008d.bin
56a416f0bdbbf806cc8ab2c520342a4b9c453473a85b61d1f91e8ce8417ad004
rtf-objdata-decoded RTF \objdata at offset 0x8D 650074 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact entropy is 7.99, consistent with packed or encrypted content.