PDF malware analysis — malicious · cd9421c332a2b90b

MALICIOUS

PDF

497.9 KB Created: 2021-08-05 11:48:07 +09:00

MD5: 6d6399e5e98164e365029a9b141e1646 SHA-1: 64f8b386000ed34f7b9f22a8144328d0e61ed31c SHA-256: cd9421c332a2b90b26152f0e85a7db621306cd1daa70f30af3210895d2aeb577

228 Risk Score

Malware Insights

MITRE ATT&CK

T1204.002 Malicious File

The PDF file contains embedded JavaScript that exploits CVE-2020-9715. The JavaScript is heavily obfuscated and appears to be a multi-stage exploit. The primary JavaScript stream (javascript_obj0052_000.js) decodes and executes further JavaScript, as indicated by the 'PDF_GENERIC_STAGE_RECOVERY' heuristic and the presence of deobfuscated JS files. This suggests a downloader or exploit loader designed to fetch and execute additional malicious content.

Machine Learning

Nyx PDF Classifier malicious score 0.9751

Heuristics 10

dataObjects ESObject stale-cache trigger — CVE-2020-9715 critical CVE exact CVE_2020_9715

PDF embeds a file and JavaScript follows the CVE-2020-9715 ESObject use-after-free trigger shape: access this.dataObjects[], clear the dataObjects entry, schedule app.setTimeOut(), then re-access the Data ESObject through toString().
PDF JavaScript exploit cluster critical PDF_JS_EXPLOIT_CLUSTER

PDF combines an executable JavaScript/action surface with exploit staging indicators such as eval/unescape/fromCharCode, XFA script content, or a related CVE pattern. Benign form JavaScript remains low-severity, but this correlated cluster is high-confidence malicious behavior.
Generic recovered JavaScript exploit stage high PDF_GENERIC_STAGE_RECOVERY

Bounded static stage recovery exposed hidden JavaScript through generic transforms such as null-byte collapse, percent decoding, marker replacement, arithmetic character codes, fromCharCode, numeric arrays, numeric-array minus-key decoders, alphabet-index arrays, /Producer half-difference metadata arrays, hex literals, marker-stripped Base64 literals, custom 6-bit XOR table decoders, or repeated-marker hex carriers. This rule is emitted only when the recovered stage contains exploit-like Acrobat JavaScript or shellcode markers.
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.
Embedded file low PDF_EMBEDDED

PDF embeds a file attachment — could carry an executable or another weaponised document as a nested payload
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)
Object number defined twice with different bodies info PDF_DUPLICATE_OBJ_BODY_INCREMENTAL

The same indirect object (N G) is defined more than once with different body bytes. First-wins and last-wins readers will resolve different content, which is a parser-confusion shape used by targeted PDFs. Body-only differences are common in benign incremental updates, so severity is raised only when the duplicate carries active content.
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.
Embedded URL info EMBEDDED_URL

One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
URL http://www.w3.org/1999/02/22-rdf-syntax-ns#
- http://ns.adobe.com/xap/1.0/
- http://purl.org/dc/elements/1.1/
- http://ns.adobe.com/xap/1.0/mm/
- http://en.wikipedia.org/wiki/MIT_License
- https://docs.microsoft.com/typography/abouthttp://lucasfonts.comMicrosoft

Extracted artifacts 9

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0052_000.js` `3898d0491023322c6c13a4fde3ddec5b1e04a346ecc32f7e2c33af1299e6d8b1`	pdf-javascript-stream	PDF /JS object 52 at offset 0x670FB	341509 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 6 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).
`generic_stage_recovery_000.js` `1c04423ffac498f1f1a4083fae7f24cd3e11100ef9c5fd7cc2150bd8aca69507`	deobfuscated-js	generic stage recovery null-collapse -> marker-DdDdDdDd-to-%u from decompressed stream at 0x1CE34 at offset 0x1CE34	26967 bytes
`generic_stage_recovery_001.js` `cdde3fccfced8f516f616a4bb9298eb54a186934e96b7911dc157a8f8941a3e1`	deobfuscated-js	generic stage recovery null-collapse -> marker-DdDdDdDd-to-%u from decompressed stream at 0x1CE34 at offset 0x1CE34	26961 bytes
`custom_b64_stage_000.js` `abbfcc7c7af618a68f4486e2b7f7f7bce60a18cba7241299b4ccd9b9a2ea8aa4`	deobfuscated-js	custom Base64 decoded JavaScript layer 1 (PDF /JS object 52) at offset 0x675A7	255159 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 4 eval/decoder/string-building token(s).
`font_00_sfnt_off00014f08.bin` `bddfb4c45a81f38bf22f598080c901088e8377b4da89f14aa7337c8ab4ac0f67`	pdf-font-stream	PDF embedded font (sfnt) at offset 0x14F08	101516 bytes
`font_01_sfnt_off0001ce34.bin` `bf072e81b3912b2a70a6dc008de28b5fc2e89b95b2b4bf5922498e0a485762bc`	pdf-font-stream	PDF embedded font (sfnt) at offset 0x1CE34	87896 bytes
`font_02_sfnt_off00025f7c.bin` `677fbd89c80e49abef805aa545a971968124a0b13c9973dba50e41708e2a27be`	pdf-font-stream	PDF embedded font (sfnt) at offset 0x25F7C	105564 bytes
`font_03_sfnt_off00031d70.bin` `9cde2b39a3c5a504c05d95977b00e3ca865b029dd5c47cf5dab68a7d1c2f8b08`	pdf-font-stream	PDF embedded font (sfnt) at offset 0x31D70	364856 bytes
`font_04_sfnt_off00052f0c.bin` `16a1f372c96d0db355b169b39ebb264afe6a3573ae07338aef0b9a2d23d145d3`	pdf-font-stream	PDF embedded font (sfnt) at offset 0x52F0C	299660 bytes

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