Malicious PDF — malware analysis report

Static analysis result for SHA-256 512ad244c58064df…

MALICIOUS

PDF

203.2 KB Created: 2021-07-21 16:04:57 +09:00
MD5: 70294ac8b61bfb936334bcb6e6e8cc50 SHA-1: f7b59f735ae76c76646617a9cc639ee591322ab2 SHA-256: 512ad244c58064dfe102f27c9ec8814f3e3720593fe1e3ed48a8cb385d52ff84
188 Risk Score

Malware Insights

MITRE ATT&CK
T1059.001 PowerShell T1204.002 Malicious File

This PDF file exploits CVE-2020-9715 using embedded JavaScript. The JavaScript, obfuscated and decoded from multiple layers, is designed to download and execute a second-stage payload. The ML classifier strongly indicates maliciousness, and the presence of exploit-related heuristics confirms the attack vector.

Machine Learning

  • Nyx PDF Classifier malicious score 0.9926

Heuristics 9

  • 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.
  • 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://ns.adobe.com/xap/1.0/rights/
    • http://ns.adobe.com/pdf/1.3/
    • http://purl.org/dc/elements/1.1/
    • http://ns.adobe.com/xap/1.0/mm/

Extracted artifacts 2

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0089_000.js
096dac3a36b1aff8e83143e48755d0fccd73cae32a33897f215d9d61c0134b70		 pdf-javascript-stream PDF /JS object 89 at offset 0x1D5F2 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).
custom_b64_stage_000.js
bc2af772cdd76cbb6d57578ba747915fbaa5723e487f595e8aa3a295741b2bde		 deobfuscated-js custom Base64 decoded JavaScript layer 1 (PDF /JS object 89) at offset 0x1DA9E 255159 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 4 eval/decoder/string-building token(s).

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