PDF malware analysis — malicious · 12267e74a91b460a

MALICIOUS

PDF

10.8 KB

MD5: 35a81179825743db26479adf162fc135 SHA-1: a52072f12fdc928df683318f7b6d0b247ba9062a SHA-256: 12267e74a91b460a876e98392b11bf8d3df34093825f149fd5f75e5e873f565c

124 Risk Score

Malware Insights

MITRE ATT&CK

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

The PDF file contains embedded JavaScript that is heavily obfuscated using String.fromCharCode. Heuristics indicate this JavaScript is designed to exploit a PDF vulnerability (PDF_JS_EXPLOIT_CLUSTER) and execute arbitrary code. The script attempts to download and execute a second-stage payload, as indicated by the calls to 'app.doc.syncAnnotScan()' and 'app.doc.getAnnots()', followed by string reconstruction and execution via 'app[fnc](buf)'. The ML classifier strongly flags this PDF as malicious.

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` `5c4d3c5f5c9aa62d51a4788e38cda53b5a5c33a7819d35f6948ef873440722b5`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x25CD	1734 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).

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