Malicious PDF — malware analysis report

Static analysis result for SHA-256 aee1cad6a7d5a440…

MALICIOUS

PDF

16.6 KB
MD5: 588f92863fa7b7aee0865c1ffed5054a SHA-1: 0a3be98497dc4079b0341ac0731e897c51d66134 SHA-256: aee1cad6a7d5a4402672f81a1268387e8ce8d95d314f0971c4d00e66c2fae52b
234 Risk Score

Malware Insights

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

The PDF file contains multiple layers of obfuscated JavaScript, including a hex decoder and incremental string building for eval. The primary exploit targets CVE-2007-5659 using the `collab.collectEmailInfo` function via `syncAnnotScan` and `getAnnots` to stage the JavaScript payload. This JavaScript is designed to download and execute further stages, indicated by the 'dropper' heuristic. The presence of multiple deobfuscated JavaScript files suggests a complex, multi-stage infection chain.

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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
javascript_obj0009_000.js
4718a27c2224fc36bf24f8e8e04598f1ad78adce4401c7be2708318738a6983d
pdf-javascript-stream PDF /JS object 9 at offset 0x3FDE 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
ac5570e9cd7bbe90478a37f60b78c46fa4e0207c7e14ea0bb4501ec65460fc90
deobfuscated-js annotation-subject callee-key decoded JavaScript at offset 0x19DF 5154 bytes
Detection
ClamAV: No threats found
Obfuscation or payload: likely
Carved artifact contains 5 eval/decoder/string-building token(s).
deobfuscated.js
88338d234b1c8b8977db37077f5fff0421d6188b51a55a9888e82f823013306d
deobfuscated-js PDF JavaScript deobfuscation pass 85367 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).