Agent skill · security · yaklang
request-smuggling
HTTP request smuggling and desynchronization testing. Use when front proxies, CDNs, or load balancers disagree with the origin on message framing (Content-Length vs Transfer-Encoding), on HTTP/2→HTTP/1 translation, or when exploring client-side desync via browser fetch pipelines.
Why this skill is useful
Adds detailed attack vectors and executable HTTP request examples for testing HTTP request smuggling vulnerabilities that are not commonly known.
What it needs
About 7k tokens when loaded. Last updated 2026-06-16. 1,563 stars on the source repository.
What this skill does
SKILL: HTTP Request Smuggling — Expert Attack Playbook AI LOAD INSTRUCTION: Expert HTTP desync techniques. Covers CL.TE, TE.CL, TE.TE obfuscation variants, HTTP/2 downgrade and pseudo-header confusion, client-side desync (browser fetch pipelines), and tool-assisted fuzzing. Assumes familiarity with raw HTTP/1.1 framing and reverse-proxy topologies. This is not “header injection” — it is message boundary disagreement between hops. Routing note: load this skill when you suspect CDN/reverse-proxy and origin disagree on request-end boundaries, or when abnormal concatenation appears during H2-to-H1 downgrade. 0. RELATED ROUTING ghost-bits-cast-attack when the HTTP client library is Apache HttpClient <= 4.5.9 (HTTPCLIENT-1974/1978) — injecting 瘍瘊 (U+760D U+760A, low bytes \r\n) into a header value causes the underlying char-to-byte writer to emit a literal CRLF, splitting the request at the origin without relying on CL/TE disagreement 1. QUICK START CL.TE first probe (front-end trusts CL, back-end trusts chunked) Assumption: front end prioritizes Content-Length, back end prioritizes Transfer-Encoding: chunked. Use a very short CL so the front end accepts a fake end, while the back end continues chunk parsing and leaves remaining bytes for the next request. Front end reads only 13 bytes based on Content-Length: 13 (that is, 0\r\n\r\nSMUGGLED, 13 bytes total) and considers the request complete. Back end parses as chunked: after the 0 end chunk, it treats SMUGGLED and onward as the start byte stream of the next request. TE.CL first probe (front-end trusts chunked, back-end trusts CL) Assumption: front end parses chunked and back end only reads Content-Length. Set CL equal to the number of bytes in the chunk-length line (commonly 4: two hex characters + \r\n), so the back end consumes only the length line and leaves the rest buffered for follow-up request splicing. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills yaklang/request-smuggling