PDF malware analysis — malicious · c29691cf4538f908

MALICIOUS

PDF

8.0 KB

MD5: 3b14fd27d9e27c47b8abaa4faed175a6 SHA-1: f83776dc73a62ac5c18720ec4bc1236dd4d2e68f SHA-256: c29691cf4538f908a02ffe6f8897594347ce848df61719b1ae67961456a90539

226 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 JavaScript/JScript T1140 Deobfuscate/Decode Files or Information

The PDF contains heavily obfuscated JavaScript, identified as a multi-stage dropper. The primary function of the script is to deobfuscate and execute a second-stage payload, as indicated by the 'PDF_JS_OBFUSCATED_DROPPER' heuristic. ClamAV detections further confirm its malicious nature. The document body was unreadable, but the script's behavior is clear: it acts as a downloader for further malicious content.

Heuristics 8

ClamAV: Pdf.Exploit.Agent-36086 critical CLAMAV_DETECTION

ClamAV detected this file as malware: Pdf.Exploit.Agent-36086
ClamAV detection on extracted artifact critical EXTRACTED_FILE_CLAMAV

ClamAV flagged at least one file extracted from inside this sample. Even when the wrapping document carries no AV detection of its own, a hit on the carved artifact is a strong indicator the sample is a delivery vehicle.
unescape() call high PDF_UNESCAPE

unescape() found — often used to decode shellcode in PDF JS exploits (matched inside decoded stream)
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, 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.
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.

Filename	Kind	Source	Size
`javascript_obj0006_000.js` `f9b4659beaf681d266cfb5046d495e7b144d406eff72e71ecd4d1451ae25ca11`	pdf-javascript-stream	PDF /JS object 6 at offset 0x143	481 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` `ecb173262cdbc8d4309a034b6ee8a649d678f76d03d2e1c22fddef15e3569df0`	deobfuscated-js	repeated-marker hex decoded JavaScript at offset 0x1AFC	1710 bytes
Detection ClamAV: No threats found Obfuscation or payload: likely Carved artifact contains 1 eval/decoder/string-building token(s).
`deobfuscated.js` `7db0665b81e48e5f08c32fc4805f087ca6647e95d4408dac43e5073df7b3033c`	deobfuscated-js	PDF JavaScript deobfuscation pass	46471 bytes
Detection ClamAV: Pdf.Exploit.Agent-36086 Obfuscation or payload: likely Carved artifact contains 4 eval/decoder/string-building token(s). Carved artifact contains 2 long base64-like blob(s).

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