PDF malware analysis — malicious · 25881e760aeed772

MALICIOUS

PDF

7.7 KB

MD5: 3fe9c2ba9c73fc133336da44016c8376 SHA-1: b955d58d95ae20dae1b207d3e78cad4607115dbe SHA-256: 25881e760aeed772b4b86569b39fe1b9cb2f7b01ec5de13b7eddf70a3a6f33d4

74 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF contains heavily obfuscated JavaScript, identified as a multi-stage dropper. The script utilizes String.fromCharCode with hex decoding and an incremental evaluation build to construct and execute its payload. This indicates a sophisticated attempt to evade static analysis and deliver a secondary malicious component. The presence of multiple deobfuscated JavaScript files suggests a complex, multi-stage infection chain.

Heuristics 6

Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 4 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_codec_loop, hex_dashed_payload, incremental_eval_build. 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.
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. (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 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0005_000.js` `852cce793efb6da930945a67e484cbb58255ac23ba75b9acf4900b180bb1bd7b`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	503 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` `30e72db7f2e66453faccdea07b3adc87cdd117e1392b897cf9085cf0eeec833a`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x197B	1743 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`deobfuscated.js` `058f7d73fdb5cddd26ca958e8b63d1246d3750ad1daadd32894d22a1a2712131`	deobfuscated-js	PDF JavaScript deobfuscation pass	23267 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 7 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).

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