PDF malware analysis — malicious · 39386d27fac7b2c9

MALICIOUS

PDF

7.9 KB

MD5: 2fdc5c7f29062c93b4fb37e30745d2b9 SHA-1: 3fd86cf35f6978a455770a9901e0d82c387c9c19 SHA-256: 39386d27fac7b2c90bd69a4fc68b0ef93ef117832d50a52a3b207fb07c499b4e

316 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 JavaScript T1204.002 Malicious File

The PDF file contains obfuscated JavaScript, indicated by multiple PDF_JAVASCRIPT and PDF_JS heuristic firings. Critical heuristics like CVE_2007_5659 and PDF_JS_OBFUSCATED_DROPPER confirm the exploitation of a known PDF vulnerability to execute a multi-stage dropper. The script's intent is to download and execute a second-stage payload, as evidenced by the deobfuscated JavaScript streams and the ML classifier's high confidence score. The specific functions and anti-analysis checks point to a sophisticated dropper mechanism.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 9

Collab.collectEmailInfo — CVE-2007-5659 critical CVE exact CVE_2007_5659

PDF 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)
ClamAV: Pdf.Exploit.Agent-36086 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-36086
ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV

ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
unescape() call high PDF_UNESCAPE

unescape() found — often used to decode shellcode in PDF JS exploits (matched inside decoded stream)
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 3 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, 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.
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 4

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0006_000.js` `f9b4659beaf681d266cfb5046d495e7b144d406eff72e71ecd4d1451ae25ca11`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	481 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` `545d5ac6eeb65bd740427377e575ad2fc2c38e3e29d79f88d06fd7185cb8c19f`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1A99	1605 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_001.js` `3a87b5cf8518235d976a6df49c27c8891bd19df24de04e72d8ca1e5f03e12d4b`	deobfuscated-js	annotation-subject callee-key decoded JavaScript at offset 0x329	4950 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s).
`deobfuscated.js` `5161433c0a8239aff2f5673f0cede804b07cdf995671efaa81680cdd7e02504b`	deobfuscated-js	PDF JavaScript deobfuscation pass	46330 bytes
Detection ClamAV: Pdf.Exploit.Agent-36086 Obfuscation or payload: likely Carved artifact contains 4 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).

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