PDF malware analysis — malicious · 163f051de774d485

MALICIOUS

PDF

8.1 KB

MD5: 67ae7888e8a3f96d5ee62a82046c85df SHA-1: 83b25fdf2445d7ee5a9d0b174a8d84fa32a70d7e SHA-256: 163f051de774d485d9440f97c3e8c26547a8be5f390c6cf617be818c7078e675

346 Risk Score

Malware Insights

MITRE ATT&CK

T1059.007 JavaScript T1203 Exploitation for Client Execution T1071.001 Web Protocols

The PDF file contains obfuscated JavaScript that leverages the syncAnnotScan and getAnnots primitives to extract an encoded payload from an annotation subject. This payload is then decoded using String.fromCharCode and evaluated, leading to the download of a second-stage shellcode from the URL http://palosantomare.com/cgi-bin/kln/z002106203r000cRab1694f9X32ba0b86Y3ad34d9eZ0100f060. The exploit targets CVE-2007-5659 and includes anti-analysis checks.

Machine Learning

Nyx PDF Classifier malicious score 1.0000

Heuristics 12

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)
Adobe Reader APSB08-13 patch-range version gate (CVE-2007-5659) high CVE likely PDF_JS_ADOBE_APSB08_13_PATCH_GATE

PDF JavaScript gates the exploit payload on (>= 8 && < 8.1.1) OR (< 7.1) — the Reader 7.0.x / 8.0–8.1.1 window patched by Adobe APSB08-13 for the CVE-2007-5659 Collab.collectEmailInfo buffer overflow. Only kits that target that exact bug check both of those patch points; benign scripts do not.
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.
Obfuscated multi-stage PDF JavaScript dropper high PDF_JS_OBFUSCATED_DROPPER

PDF JavaScript shows 3 independent signals of exploit-kit-style multi-stage obfuscation: annot_subject_stage, hex_dashed_payload, 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.
PDF JavaScript shellcode contains an embedded download URL high PDF_JS_SHELLCODE_DOWNLOAD_URL

Decoded PDF JavaScript shellcode contains a hardcoded http(s) URL stored as little-endian %uXXXX Unicode escapes. Reader exploit shellcode embeds the second-stage fetch URL this way and pulls it down with a urlmon/URLDownloadToFile-style download-and-execute (commodity downloader behaviour rather than a specific Acrobat CVE).
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.
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://palosantomare.com/cgi-bin/kln/z002106203r000cRab1694f9X32ba0b86Y3ad34d9eZ0100f060

Extracted artifacts 5

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`javascript_obj0005_000.js` `9d5c7e01faed5b04e9ec11f1d98b73f0012c871beaf60e9f9d32ad6df00d46f7`	pdf-javascript-stream	PDF /JS object 5 at offset 0x148	550 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`generic_stage_recovery_000.js` `f4775ec9df865063984a555e0731e5ff26e73ddb98c144fce7fab43f6ef2965c`	deobfuscated-js	generic stage recovery split-literal-normalize from JavaScript object 5 at offset 0x148	545 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_000.js` `e1d91043832222843d9e78e28511e059aeff05bc9d9030898a96ffe8c4911394`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1B54	1693 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`legacy_pdfkit_stage_001.js` `a270671cf2ceec937e0e24a2b60e96572529cb4fb14a77488d78715ee91a12fa`	deobfuscated-js	annotation-subject callee-key decoded JavaScript at offset 0x359	5065 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 5 eval/decoder/string-building token(s).
`deobfuscated.js` `479d911bdbbfc562d4d9cc047bc3c38804a015d97ac4b654dc5053ba1989d15c`	deobfuscated-js	PDF JavaScript deobfuscation pass	23176 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 2 eval/decoder/string-building token(s). Carved artifact contains 1 long base64-like blob(s).

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