Malware Insights
The PDF document contains obfuscated JavaScript, identified as a multi-stage dropper. The critical heuristic 'CVE_2007_5659: Collab.collectEmailInfo' indicates the exploitation of a known vulnerability to execute this script. The script's primary function appears to be downloading and executing a second-stage payload, as suggested by the 'PDF_JS_OBFUSCATED_DROPPER' firing. The extensive obfuscation and multi-stage nature point towards a sophisticated downloader, but without further stages or network activity, the exact family remains undetermined.
Heuristics 9
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Collab.collectEmailInfo — CVE-2007-5659 critical CVE exact CVE_2007_5659PDF JavaScript calls Collab.collectEmailInfo — CVE-2007-5659 is a buffer overflow in Adobe Reader triggered by a long argument or heap-sprayed message field passed to Collab.collectEmailInfo(). Part of a series of Acrobat JS API exploits. (identified after JavaScript deobfuscation)
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ClamAV: Pdf.Exploit.Agent-35901 critical CLAMAV_DETECTIONClamAV detected this file as malware: Pdf.Exploit.Agent-35901
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Annotation subject callee-key hex JavaScript stager high PDF_ANNOT_SUBJECT_CALLEE_HEX_STAGERPDF JavaScript uses syncAnnotScan()/getAnnots() to read an indirect annotation /Subject stream, percent-decodes it through marker replacement, then uses a callee.toString()-derived key to decode and eval the final exploit stage.
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Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPERPDF JavaScript shows 4 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_codec_loop, 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.
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JavaScript action low PDF_JAVASCRIPTPDF contains a /JavaScript action. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
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Embedded JS stream low PDF_JSPDF references a /JS stream. Generic JavaScript is common in benign forms; specific dangerous APIs are scored by separate rules.
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String.fromCharCode low PDF_FROMCHARCODEString.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)
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syncAnnotScan annotation-staging primitive low PDF_FOXIT_SYNCANNOTSCANPDF 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)
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Suspicious extracted artifact info EXTRACTED_FILE_STATIC_TRIAGEOne 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 4
Files carved from inside the sample during analysis.
| Filename | Kind | Source | Size |
|---|---|---|---|
javascript_obj0009_000.js4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d |
pdf-javascript-stream | PDF /JS object 9 at offset 0x3F82 | 469 bytes |
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Detection
ClamAV:
No threats found
Obfuscation or payload:
likely
Carved artifact contains 1 eval/decoder/string-building token(s).
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annotation_subject_callee_hex_stage_000.js4e7174c5970622a44b3e47bd83c7885b96f2288f8c2ef68fe4f9d7fd2ea10f3a |
deobfuscated-js | annotation-subject callee-key decoded JavaScript at offset 0x1991 | 5100 bytes |
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Detection
ClamAV:
No threats found
Obfuscation or payload:
likely
Carved artifact contains 5 eval/decoder/string-building token(s).
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legacy_pdfkit_stage_000.jsd2ff81558a67fdb95f65aa8a283ccad2eb090644a68af0b01f3092fc57cbba44 |
deobfuscated-js | repeated-marker hex decoded JavaScript at offset 0x19E5 | 11746 bytes |
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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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deobfuscated.jsdab69ac31354b9fef9b80202cc0e66491a8f631343d60a69ea3327e6e62e1655 |
deobfuscated-js | PDF JavaScript deobfuscation pass | 90211 bytes |
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Detection
ClamAV:
No threats found
Obfuscation or payload:
likely
Carved artifact contains 10 eval/decoder/string-building token(s). Carved artifact contains 3 long base64-like blob(s).
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