PDF malware analysis — malicious · fbba7e95590dd542

MALICIOUS

PDF

15.5 KB

MD5: 98defb5b6ad0c421f3fba89bfea39bf6 SHA-1: aeedc0eddeea3e2ad93d4e6971b1b17135adfbe0 SHA-256: fbba7e95590dd542b19d831af08742fbb629c0255f457171af154865d003a217

124 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF contains multiple embedded JavaScript streams, including one that uses String.fromCharCode and another that appears to be an eval stager. These scripts are designed to deobfuscate and execute further malicious code, likely downloading and running a second-stage payload. The ML classifier strongly indicates maliciousness, and the heuristics point to common PDF exploitation techniques.

Machine Learning

Nyx PDF Classifier malicious score 0.9999

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` `42077b420102e9cffdc93539ce92409eefe278adc8f70b28e8ef1bc5b5817e8a`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1A94	12036 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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