PDF malware analysis — malicious · 39cf7f56c0eadf5b

MALICIOUS

PDF

7.9 KB

MD5: 2e9fa3d88cfc8a25e6b4786f3990164b SHA-1: b0c330b5b5c680a048067e737310fb6aebba5959 SHA-256: 39cf7f56c0eadf5b0d564f4885b5eea654b670818af903a8cecff062d4180d50

134 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The PDF contains obfuscated JavaScript, identified as a multi-stage dropper. This script utilizes techniques like `String.fromCharCode` with hex decoding and incremental evaluation to build and execute its payload. The high-confidence heuristic 'PDF_JS_OBFUSCATED_DROPPER' and ClamAV detection 'Pdf.Exploit.Agent-35902' strongly indicate malicious intent. The primary function appears to be downloading and executing a secondary payload, though the specific URL is not directly extractable from the provided evidence.

Heuristics 7

ClamAV: Pdf.Exploit.Agent-35902 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-35902
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` `3cf6a22459cda11e607fc9e0dc0c88d01a8425e26488ff87df38d855ceb4dccf`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	465 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` `b29376b3455cd2210e6950eb8cff00da0baaa30fb13c45e135a633ed70645c71`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1A74	1905 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`deobfuscated.js` `7d6d48d836ed757b672ea7efdb5354e688db00c6f8e316fc3acd607c87c8995a`	deobfuscated-js	PDF JavaScript deobfuscation pass	25298 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).

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