PDF malware analysis — malicious · cf73fbd33178dfb1

MALICIOUS

PDF

16.6 KB

MD5: aa04bd08b53b98b6e59d4bf5092b6ead SHA-1: bfd4754653c19ea8d0dd2ac5ec979780647adeff SHA-256: cf73fbd33178dfb11f9eea7f8d643cadadd30e27cf008024c961d7679d1713b5

234 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 JavaScript/JScript T1204.002 Malicious File

The PDF file contains multiple embedded JavaScript streams, heavily obfuscated and employing techniques like String.fromCharCode with hex decoding. The critical heuristic CVE_2007_5659 indicates exploitation of a known PDF vulnerability via the syncAnnotScan primitive to execute a JavaScript stager. This stager is designed to download and execute further malicious content, as suggested by the 'Obfuscated multi-stage PDF JavaScript dropper' heuristic. The presence of multiple deobfuscated JavaScript files further supports a multi-stage attack.

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 0x3FE5	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` `348d8ba13c4f08254eba597777fd4e657c2c52c9cc3a681fc73a94d581bfeb53`	deobfuscated-js	annotation-subject callee-key decoded JavaScript at offset 0x19EE	5185 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` `989048137794afd9157098f3ec3898b00f2721d84dc76208b24d136ebf6a27fb`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1A42	11578 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` `05cc772912f5141ddd40c84926328e5c59a1dd9b310121d2f79dbf352ca915e1`	deobfuscated-js	PDF JavaScript deobfuscation pass	124121 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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