PDF malware analysis — malicious · 0240e4f586c44dfc

MALICIOUS

PDF

11.1 KB

MD5: e097baccb1387a5e3e78c207c78b76ca SHA-1: b467d0a61001b9f1b31964fab8085bc69bd8395b SHA-256: 0240e4f586c44dfca9c6a78581a09ba3fa9fc8686d6d64167c1cb5cbed8d960c

124 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1203 Exploitation for Client Execution T1566.001 Spearphishing Attachment

The PDF sample contains embedded JavaScript that is obfuscated using character codes. Heuristics indicate this JavaScript is designed to exploit a PDF vulnerability (PDF_JS_EXPLOIT_CLUSTER) and execute code. The script attempts to reconstruct a string using `String.fromCharCode` and then execute it via `app[fnc](buf)`, likely downloading and running a secondary payload. The ML classifier strongly indicates maliciousness.

Machine Learning

Nyx PDF Classifier malicious score 0.9999

Heuristics 6

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.
JavaScript action low 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.
String.fromCharCode low PDF_FROMCHARCODE

String.fromCharCode found — used to construct payload strings dynamically. Common in benign JavaScript libraries for codepoint manipulation, so this alone is informational; weaponised use is also caught by the dedicated fromCharCode-stage and exploit-shape rules. (matched inside decoded stream)
syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCAN

PDF JavaScript calls syncAnnotScan() — a no-op annotation-enumeration primitive used by exploit-kit JavaScript to stage payload reads from annotation /Subject fields before eval(). Not a vulnerable sink itself; rarely seen in legitimate PDFs. (identified after JavaScript deobfuscation)
Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGE

One or more files extracted from inside this sample matched static suspicious-content checks such as script obfuscation, encoded payload blobs, packed data, or execution/download terms.

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0004_000.js` `be4694a17eb89a55f7eb3db389ba2bc4f102f4c7dcfc99549d848cdb7df5dfb5`	pdf-javascript-stream	PDF /JS object 4 at offset 0xE1	1940 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`numeric_charcode_stage_000.js` `6c41320119e160dc719997b9a2efb3600ea9d7e9d7e44b4dc2125762dc9f365f`	deobfuscated-js	numeric char-code string decoded JavaScript at offset 0xEF	505 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_000.js` `53508dcaa7e1b10d118cdbfb2fb8aa640731d559057d5e312f8c366c1030f745`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x2718	1887 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).

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