PDF malware analysis — malicious · 694cf8a0d87cf527

MALICIOUS

PDF

20.3 KB

MD5: 8c756f5504caceb9719a7d152b84445b SHA-1: 76da6eab99ee07e3c330c05bd14c020c6f358079 SHA-256: 694cf8a0d87cf5274d40d939175a9d20860382f5c6f29ea11f514b4f7631d2ef

124 Risk Score

Malware Insights

MITRE ATT&CK

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

This PDF file contains obfuscated JavaScript that leverages PDF viewer vulnerabilities, specifically targeting the syncAnnotScan primitive and using String.fromCharCode to decode exploit code. The script attempts to download and execute a second-stage payload, indicated by the ML_NYX_PDF_MALICIOUS heuristic and the PDF JavaScript exploit cluster firing. The exact URL for the payload download is not directly visible due to obfuscation, but the mechanism is clear.

Machine Learning

Nyx PDF Classifier malicious score 0.9998

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 2

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0004_000.js` `b771a67801a2a024471cb29d8ce119b13dc98b5c56ef213dece7e1a5cc7b8bed`	pdf-javascript-stream	PDF /JS object 4 at offset 0xE1	1814 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` `4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d`	deobfuscated-js	numeric char-code string decoded JavaScript at offset 0xEF	469 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).

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