PDF malware analysis — malicious · 8136f299e9cb3864

MALICIOUS

PDF

15.5 KB

MD5: 7f3d56a93bd6402a31b7154a4ec372c8 SHA-1: 546e5353576b48612f568a056b6a7e35eb32b7a4 SHA-256: 8136f299e9cb3864e94b6f4988f377fb3c3088dddf7d38c05ea5e5f2359be02f

94 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 JavaScript/JScript T1566.002 Spearphishing Attachment

The PDF file contains multiple embedded JavaScript streams, indicated by the PDF_JAVASCRIPT and PDF_JS heuristics. The PDF_ANNOT_SUBJECT_HEX_EVAL_STAGER heuristic specifically points to an annotation subject being used to decode and execute a stager. The extracted JavaScript files, particularly 'numeric_charcode_stage_000.js', are likely responsible for further deobfuscation and execution of malicious code, potentially downloading additional payloads. The confidence is slightly reduced due to the lack of explicit URL IOCs in the provided evidence, but the presence of multiple JavaScript stages strongly suggests a downloader or dropper functionality.

Heuristics 6

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 3

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` `c7c34e75074d1a9b4e27e09d4d22882e483b81ddbe8d1decf1ee440dfc55208d`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1A73	12133 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).

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