In early 2024, security researchers flagged a severe vulnerability in Open Robotics’ popular Robotic Operating System 2 (ROS2) and the Navigation2 (Nav2) stack, specifically affecting Humble versions. Registered as CVE-2024-25197, this flaw allows an attacker to crash mission-critical navigation nodes via a NULL pointer dereference in the isCurrent() function located at src/layered_costmap.cpp. Such crashes could disrupt robots in safety-sensitive environments, from warehouses to hospitals.

In this long-read, I’ll break down the vulnerability in plain English, show you a simplified exploit, and link the main references. By the end, you’ll see why patching is urgent and learn practical steps to safeguard your robots.

What is ROS2 & Nav2?

ROS2 is a set of libraries and tools to help software developers build robot applications. The Nav2 project is used for mobile robot navigation—think of robots moving around factories or hospitals.

“*Humble*” is the codename for a LTS (Long-Term Support) version released by Open Robotics.

Where’s the Bug?

- File: src/layered_costmap.cpp

Function: isCurrent()

The function is responsible for checking if all the navigation costmap layers are up-to-date. But under some error conditions, it is called when some layer objects are not (properly) initialized—that is, they are NULL pointers in C++.

Accessing a method on a NULL pointer causes a crash—a “NULL pointer dereference.”

Reproducing the Flaw (Code Snippet)

Let’s look at an abbreviated, simplified snippet—note: details may vary in the actual Nav2 source.

// src/layered_costmap.cpp

bool LayeredCostmap::isCurrent() const {
  for (auto* plugin : plugins_) {
    // plugin could be a nullptr here!
    if (!plugin->isCurrent()) {
      return false;
    }
  }
  return true;
}

If, due to an error elsewhere (like a failed plugin load), one of the pointers in plugins_ is nullptr, this function will call isCurrent() on a NULL pointer, leading to a segmentation fault.

How could an attacker exploit this?

An attacker (or even a buggy configuration) could cause a costmap plugin to fail loading or unload in an unexpected way—leaving a nullptr in the plugins list. When the costmap node tries to check if the system is “current,” a crash occurs.

Demo in pseudocode

# For a robot operator or attacker with access to ROS2 configs

# Intentionally misconfigure costmap plugin:
costmap_plugins:
  - name: "NonexistentPlugin"
    type: "nonexistent/NonexistentLayer"

# Launch navigation with ros2 launch <...>
# The fault will leave a nullptr in plugins_.
# When LayeredCostmap::isCurrent() is called, ROS2 navigation node will crash.

Or, in a simulated malicious plugin

class NullPlugin : public nav2_costmap_2d::Layer {
  // Overridden methods, possibly failing init
};

void inject_null_plugin() {
  // Append a nullptr to the 'plugins_' vector in layered_costmap
  layered_costmap->plugins_.push_back(nullptr);
}

Safety Risk: Abrupt stops could endanger people (e.g. service robots in hospitals).

- Reliability: Any robot depending on Nav2 for movement or obstacle avoidance can unexpectedly fail.

The Patch

A safe fix: check for NULL before dereferencing!

bool LayeredCostmap::isCurrent() const {
  for (auto* plugin : plugins_) {
    if (plugin == nullptr) {
      // Log warning, skip, or handle as needed
      continue; // or return false;
    }
    if (!plugin->isCurrent()) {
      return false;
    }
  }
  return true;
}

Merged Patch:
Actual patch diff (example, not verbatim)
GitHub Patch Example (replace XXX with actual PR id when available)

How to Fix

- Update your ROS2/Nav2 installations to the latest *Humble* patch.

References & Resources

- CVE database entry: CVE-2024-25197
- Nav2 Source Code: Nav2 on GitHub
- Patch commit / PR: Sample Pull Request
- Community forum discussion: ROS Answers thread (replace with actual Q ID)

Conclusion

CVE-2024-25197 shows how a tiny programming oversight can have major real-world impact in robotics. As critical infrastructure increasingly uses robots, updating and testing against these kinds of bugs is crucial to safety, reliability, and security.

If you run mobile robots with ROS2 Nav2 Humble, patch NOW—before a crash ends up putting your fleet out of action.


*This post is a unique synthesis for practical understanding. For full disclosure information, always consult the official CVE entry and the Nav2 repo.*

Timeline

Published on: 02/20/2024 14:15:09 UTC
Last modified on: 10/29/2024 20:35:16 UTC