IBM Langflow OSS Unauthenticated RCE via PythonCodeStructuredTool exec() in Public Flow Build Endpoint

#!/usr/bin/env bash
# CVE-2026-10134 Checker — IBM Langflow OSS PythonCodeStructuredTool RCE
# Checks whether a Langflow instance is running a vulnerable version
# and whether the unauthenticated build_public_tmp endpoint is reachable.
#
# Usage:  ./check_cve_2026_10134.sh <LANGFLOW_BASE_URL>
# Example: ./check_cve_2026_10134.sh https://langflow.example.com:7860
#
# Exit codes:
#   0 = PATCHED    (version >= 1.10.0)
#   1 = VULNERABLE (version < 1.10.0)
#   2 = UNKNOWN    (could not determine version)
#   3 = usage error

set -euo pipefail

FIXED_VERSION="1.10.0"
TARGET="${1:-}"

if [[ -z "$TARGET" ]]; then
  echo "Usage: $0 <LANGFLOW_BASE_URL>"
  echo "Example: $0 https://langflow.example.com:7860"
  exit 3
fi

# Strip trailing slash
TARGET="${TARGET%/}"

echo "[*] CVE-2026-10134 checker for IBM Langflow OSS"
echo "[*] Target: $TARGET"
echo "[*] Fixed in: >= $FIXED_VERSION"
echo ""

# --- Step 1: Fetch version from API ---
echo "[*] Querying /api/v1/version ..."
VERSION_RAW=$(curl -sk --connect-timeout 10 --max-time 15 \
  "${TARGET}/api/v1/version" 2>/dev/null) || {
  echo "[!] Could not reach ${TARGET}/api/v1/version"
  echo "[!] The instance may be down, unreachable, or require authentication."
  echo "UNKNOWN"
  exit 2
}

# Parse version — try jq first, fall back to grep
if command -v jq &>/dev/null; then
  VERSION=$(echo "$VERSION_RAW" | jq -r '.version // empty' 2>/dev/null)
else
  VERSION=$(echo "$VERSION_RAW" | grep -oP '"version"\s*:\s*"\K[^"]+' 2>/dev/null || true)
fi

if [[ -z "$VERSION" ]]; then
  echo "[!] Could not parse version from API response."
  echo "[!] Raw response: $VERSION_RAW"
  echo "UNKNOWN"
  exit 2
fi

echo "[+] Detected Langflow version: $VERSION"

# --- Step 2: Probe the vulnerable endpoint ---
echo "[*] Probing /api/v1/build_public_tmp/ endpoint ..."
DUMMY_UUID="00000000-0000-0000-0000-000000000000"
PUBFLOW_STATUS=$(curl -sk -o /dev/null -w '%{http_code}' \
  --connect-timeout 10 --max-time 15 \
  "${TARGET}/api/v1/build_public_tmp/${DUMMY_UUID}/flow" \
  -X POST -H 'Content-Type: application/json' -d '{}' 2>/dev/null) || PUBFLOW_STATUS="000"

if [[ "$PUBFLOW_STATUS" == "404" ]]; then
  echo "[+] build_public_tmp endpoint returned 404 (endpoint may be removed or blocked)"
elif [[ "$PUBFLOW_STATUS" == "000" ]]; then
  echo "[?] Could not reach build_public_tmp endpoint (connection failed)"
else
  echo "[-] build_public_tmp endpoint responded with HTTP $PUBFLOW_STATUS (endpoint EXISTS)"
fi

# --- Step 3: Version comparison ---
version_gte() {
  # Returns 0 if $1 >= $2 using sort -V
  printf '%s\n%s' "$2" "$1" | sort -V -C 2>/dev/null
}

echo ""
if version_gte "$VERSION" "$FIXED_VERSION"; then
  echo "[+] Version $VERSION >= $FIXED_VERSION"
  echo "PATCHED"
  exit 0
else
  echo "[-] Version $VERSION < $FIXED_VERSION"
  if [[ "$PUBFLOW_STATUS" != "404" && "$PUBFLOW_STATUS" != "000" ]]; then
    echo "[-] WARNING: build_public_tmp endpoint is reachable (HTTP $PUBFLOW_STATUS)"
    echo "[-] This instance is likely exploitable via CVE-2026-10134."
  fi
  echo "VULNERABLE"
  exit 1
fi