PDF malware analysis — malicious · 653ca132660c310a

MALICIOUS

PDF

17.5 KB

MD5: 87078c7ad8e22e4799c7dfa58ef1a719 SHA-1: 0f1eb2006033e3198daa7b12f92835d9de6f6cf6 SHA-256: 653ca132660c310a3b5cd5cfeedb6c439f003b17bb92b4a96c8fa587125ead3d

184 Risk Score

Malware Insights

MITRE ATT&CK

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

This PDF file contains embedded JavaScript that is heavily obfuscated using character codes and string concatenation. The script's primary function appears to be decoding and executing a second-stage payload, likely leveraging a known PDF exploit. The ML classifier strongly indicates maliciousness, and the heuristics point to a JavaScript exploit cluster within the PDF.

Machine Learning

Nyx PDF Classifier malicious score 0.9999

Heuristics 7

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.
Annotation subject hex-decoded eval stager critical PDF_ANNOT_SUBJECT_HEX_EVAL_STAGER

PDF OpenAction JavaScript decodes a decimal char-code launcher, enumerates annotation subjects with syncAnnotScan()/getAnnots(), turns dash-delimited hex bytes into JavaScript with String.fromCharCode(), and evals the staged result. This is an exploit-kit delivery pattern and not normal PDF form logic.
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 4

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).
`legacy_pdfkit_stage_000.js` `ca53d737bc9e13cbe9314e04d6d2f4aaf3125c32c0b74b4fc81b7c25ef6efe17`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x232F	11827 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).
`legacy_pdfkit_stage_001.js` `c122b9ef45b76224a58be2a6ff15a5ae74244eb96dc0c40310d50b58675628f7`	deobfuscated-js	nested inline base-23 callee-key decoded JavaScript at offset 0x232F	4649 bytes

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