PDF malware analysis — malicious · 75828cda19d3abe6

MALICIOUS

PDF

16.4 KB

MD5: 2e85f308a3573fb919860f9367c8a36d SHA-1: 64d55ab6ba199bb7e6d194bea40eb78d4a84248c SHA-256: 75828cda19d3abe6c37ce96fcd711bb9501d82ca0aebcc86a4a835af3939ef38

136 Risk Score

Malware Insights

MITRE ATT&CK

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

This PDF file contains obfuscated JavaScript designed to evade analysis and download a secondary payload. The script utilizes anti-analysis techniques such as checking app.plugIns.length and employs string manipulation to construct its execution logic. The primary function appears to be retrieving encoded data from annotation subjects and executing it, indicating a dropper functionality.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 6

Generic recovered JavaScript exploit stage high PDF_GENERIC_STAGE_RECOVERY

Bounded static stage recovery exposed hidden JavaScript through generic transforms such as null-byte collapse, percent decoding, marker replacement, arithmetic character codes, fromCharCode, numeric arrays, numeric-array minus-key decoders, alphabet-index arrays, /Producer half-difference metadata arrays, hex literals, marker-stripped Base64 literals, custom 6-bit XOR table decoders, or repeated-marker hex carriers. This rule is emitted only when the recovered stage contains exploit-like Acrobat JavaScript or shellcode markers.
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 3 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_dashed_payload, repeated_pluginschk. This is strongly consistent with pre-2011 Adobe Reader PDF droppers — OpenAction JS reads encoded data from annotation subjects, decodes it through one or more hex / base-N loops, and invokes eval indirectly (method name built one character at a time). The actual CVE is hidden in the final decoded layer and is not visible via static analysis.
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.
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. (matched in decompressed stream)
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 5

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0005_000.js` `a3319192cac6d4dc4eeb6af2d736b0ffec979b23116a003bc7c23382761c32a5`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	733 bytes
`generic_stage_recovery_000.js` `d0d9b30997e09d7380aa1f50db3a2ef0c80cafe011beab0224533da2964e68f5`	deobfuscated-js	generic stage recovery split-literal-normalize from JavaScript object 5 at offset 0x148	717 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` `227bf681824c7d1721d6dc0bc2bf8726da78e953b405e64a1e6666ba38052127`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1BF0	12847 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` `6cf29ededf2a8c2208aa20ad19cfab6eed0b35d2dbd402a25ea73bac90ee2213`	deobfuscated-js	nested inline base-23 callee-key decoded JavaScript at offset 0x1BF0	5126 bytes
`deobfuscated.js` `f323db5b9d07249840465e2193cdac832b246a9424d4d3ff4376dfa38aa7e7de`	deobfuscated-js	PDF JavaScript deobfuscation pass	99560 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 long base64-like blob(s).

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