PDF malware analysis — malicious · 31ee9b5698271a50

MALICIOUS

PDF

17.3 KB

MD5: c8b8535c4f1126bffc19a1cdcfd23995 SHA-1: cc83a109de33269dcce63729dae35b6e7f238f5a SHA-256: 31ee9b5698271a5013d2609b8e19be2b3569e2d45716dba352a1112b0bde5b1d

234 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 JavaScript/JScript T1204.002 Malicious File T1071.001 Web Protocols

The PDF file contains heavily obfuscated JavaScript, identified by multiple high and critical heuristic firings including 'PDF_JS_OBFUSCATED_DROPPER' and 'CVE_2007_5659'. The script leverages the 'Collab.collectEmailInfo' method and a hex decoder to execute a stager. This stager is designed to download and execute a second-stage payload, indicated by the 'PDF_FROMCHARCODE' and 'PDF_ANNOT_SUBJECT_CALLEE_HEX_STAGER' rules. The presence of ClamAV detection further confirms its malicious nature.

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.
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 4

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 0x42DF	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` `a393a993f3954041364c9725370f48527cff87704d1dd002cef5f7dcdc7cc2a9`	deobfuscated-js	annotation-subject callee-key decoded JavaScript at offset 0x1B1E	5425 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_000.js` `c2ed11c046a7a2dcdfc08c7d87cd406e174a3445fd1102f9b8fa239f33aae768`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1B72	12136 bytes
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).
`deobfuscated.js` `ca25c12ca0f5dbefee2bf9875d1d28b718c5bea78b178ee05d38ca24ea900858`	deobfuscated-js	PDF JavaScript deobfuscation pass	146046 bytes
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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