Individual skill

ghost-bits-cast-attack

Java "Ghost Bits" / Cast Attack playbook (Black Hat Asia 2026). Use when attacking Java services where 16-bit char is silently narrowed to 8-bit byte to bypass WAF/IDS for SQL injection, deserialization RCE, file upload (Webshell), path traversal, CRLF injection, request smuggling, and SMTP injection. Affects Tomcat, Spring, Jetty, Undertow, Vert.x, Jackson, Fastjson, Apache Commons BCEL, Apache HttpClient, Angus Mail, JDK HttpServer, Lettuce, Jodd, XMLWriter and re-enables many "patched" CVEs through WAF bypass.

skills/ghost-bits-cast-attack/SKILL.md

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Last checked: Nov 2, 2026

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Repository stars (not skill ratings): 2,633
Repository last updated: Sep 13, 2026
License: MIT

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data Derived category
security Derived category
data-databases Derived category
security-application Derived category

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PAYLOAD_COOKBOOK.mddoc · 24,488 bytes
SKILL.mdcore · 30,693 bytes
SKILL.mdcore · 30,693 bytes
SKILL.mdcore · 30,693 bytes

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# SKILL: Ghost Bits / Cast Attack — Java char to byte Narrowing Playbook

> **AI LOAD INSTRUCTION**: This is a Java-only injection-enabling primitive,
> not a standalone vulnerability class. Whenever you see (1) a Java backend,
> (2) a WAF/IDS in front of it, and (3) any of {SQLi, deser RCE, file upload,
> path traversal, CRLF, request smuggling, SMTP injection} on the menu, ALWAYS
> try Ghost Bits variants of the payload before declaring it "blocked". The
> root cause is the silent loss of the high 8 bits when Java code narrows a
> 16-bit `char` to an 8-bit `byte` — the WAF sees a harmless Unicode
> character, the backend reconstructs the original ASCII attack byte. Base
> models almost never reach for this primitive.
>
> Source: Black Hat Asia 2026 talk *Cast Attack: A New Threat Posed by Ghost
> Bits in Java* by Xinyu Bai (@b1u3r), Zhihui Chen (@1ue), with contributor