PDF malware analysis — malicious · b6666f79bb042c01

MALICIOUS

PDF

16.8 KB

MD5: 65e39c76a20d02375b5e55095aa6d1e1 SHA-1: e4bf16ef5ba81f4150dc896fd6eb7171a6c26667 SHA-256: b6666f79bb042c015255eb48080934dc5944fa6856173a634e9f97c5871290a3

284 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell T1204.002 Malicious File

The PDF utilizes the 'Collab.collectEmailInfo' method, a known vulnerability for CVE-2007-5659, to launch obfuscated JavaScript. This JavaScript is a multi-stage dropper that decodes and executes further stages, ultimately aiming to download and execute a second-stage payload. The presence of multiple deobfuscated JavaScript files and the 'Pdf.Exploit.Agent-35901' ClamAV signature strongly indicate malicious intent.

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-35901 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-35901
Annotation subject callee-key hex JavaScript stager high PDF_ANNOT_SUBJECT_CALLEE_HEX_STAGER

PDF 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.
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF 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.
Suspicious extracted artifact high 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.
String.fromCharCode medium PDF_FROMCHARCODE

String.fromCharCode found — used to construct payload strings dynamically (matched inside decoded stream)
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)

Extracted artifacts 3

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0009_000.js` `4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d`	pdf-javascript-stream	PDF /JS object 9 at offset 0x40B8	469 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`annotation_subject_callee_hex_stage_000.js` `61c08b45adbaaac3273bfb9d004b56f635d54997b2c0497d3e8497d4e56bcd65`	deobfuscated-js	annotation-subject callee-key decoded JavaScript at offset 0x19A9	5123 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s).
`deobfuscated.js` `28018302ae74a2cc8e0f34cb3d913b7c95c661d4e0376bd5397e87e699951b9e`	deobfuscated-js	PDF JavaScript deobfuscation pass	93259 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 6 eval/decoder/string-building token(s). Carved artifact contains 3 long base64-like blob(s).

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