PDF malware analysis — malicious · d9816182ad944944

MALICIOUS

PDF

8.1 KB

MD5: 91d4d89b5895e2528e66cb70257142d5 SHA-1: 2effaa32e8bced889f7b864a6927e851f97dba97 SHA-256: d9816182ad9449446dc533dddf9b51ea4cd715774705f77fd100f8eaafdae80a

134 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The sample is a PDF file that contains obfuscated JavaScript. Heuristics indicate this JavaScript acts as a multi-stage dropper, decoding a payload from an annotation subject and executing it. The ClamAV detection 'Pdf.Exploit.Agent-35916' further confirms its malicious nature. The primary attack vector appears to be exploiting a PDF vulnerability to achieve arbitrary code execution.

Heuristics 7

ClamAV: Pdf.Exploit.Agent-35916 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-35916
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 5 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_codec_loop, hex_dashed_payload, incremental_eval_build, 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.
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` `6c41320119e160dc719997b9a2efb3600ea9d7e9d7e44b4dc2125762dc9f365f`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	505 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` `87031b7f905f88e3070280e9df36a09c90d0d2744a1301bf151f0d68c251cacd`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1B33	1818 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`deobfuscated.js` `05999ddf2f75dc4edb234248e14e793a533ead7b89d0e03a37f9d101bc8e3bbc`	deobfuscated-js	PDF JavaScript deobfuscation pass	27860 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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