PDF malware analysis — malicious · 51dba3b26923b70f

MALICIOUS

PDF

17.0 KB

MD5: a1dd36def3f57f4837e1acd6d22c5b9b SHA-1: 7c92374db4aef3f90385287fc1302eeeabf75efd SHA-256: 51dba3b26923b70f1ddd847e698488fdd8541ec24930db2c2c817cb19c117bd5

234 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 JavaScript T1204.001 Malicious Link

The PDF file contains obfuscated JavaScript that leverages the Collab.collectEmailInfo method (CVE-2007-5659) to execute a stager. This stager is designed to download and execute a second-stage payload, as indicated by the 'PDF_JS_OBFUSCATED_DROPPER' and 'PDF_ANNOT_SUBJECT_CALLEE_HEX_STAGER' heuristics. 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 0x418E	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` `48cd0bdb77917b9a691e912d5d6797df2b07b346bd1cd7916ea6ac2fe2b868bd`	deobfuscated-js	annotation-subject callee-key decoded JavaScript at offset 0x1AA2	5328 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` `7c958fa72c696345fdb56fc530b783084d63392cda77141f4ef71688b68cfe9a`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1AF6	11880 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` `da882f8b2a366173e7c5b9b68e9093ed603a3db64df6ead6f2741ea0608b2f25`	deobfuscated-js	PDF JavaScript deobfuscation pass	90993 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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