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CVE-2024-21626 is a critical container escape vulnerability residing within the runc container runtime, which is heavily utilized by enterprise platforms like Docker and Kubernetes.
The flaw fundamentally stems from an internal file descriptor leak occurring during the container spawning process.
Specifically, certain internal file descriptors, including those pointing to host filesystem directories such as the cgroup root, remain open and accessible to the newly spawned container process.
When a container is initialized with a specially crafted working directory referencing these leaked file descriptors, the working directory resolves outside the intended container isolation boundary.
An attacker can exploit this behavior by manipulating the container image or build context, setting the working directory to a procfs file descriptor path like /proc/self/fd/.
Once the container process starts with its working directory set to a host-level path, directory traversal sequences can be executed.
By navigating upward using relative path components, the container process gains direct read and write access to the underlying host filesystem.
This breach shatters the container security sandbox, allowing malicious actors to read sensitive system files, manipulate host binaries, or execute arbitrary code.
Because container runtimes frequently execute with high privileges, compromising the underlying host via this vector typically results in full root-level host system compromise.
Multi-tenant environments are particularly at risk, as an escape from a single isolated container can cascade into complete infrastructure takeover.
Mitigation requires updating runc to patched versions and avoiding untrusted image builds.
DailyCVE Form:
Platform: Docker runc
Version: 1.1.11 prior
Vulnerability: File descriptor leak
Severity: Critical score
date: 2024-01-31
Prediction: Released February 2024
What Undercode Say:
To analyze and verify the container environment, administrators can execute specific diagnostic and status commands via bash.
docker version runc --version cat /proc/self/cgroup ls -la /proc/self/fd/
These commands inspect runtime versions, cgroup memberships, and active file descriptors to check for potential leakage points.
Exploit: (Educational Purposes!)
An attacker crafts a malicious Dockerfile specifying a leaked file descriptor path as the working directory.
FROM ubuntu:latest WORKDIR /proc/self/fd/9 RUN ../../../../../bin/sh -c "cat /etc/shadow"
When built or executed, the container traverses outside its root directory into the host filesystem.
Protection: from this CVE
To secure systems against CVE-2024-21626, administrators must immediately update the runc package to version 1.1.12 or later.
Container images from untrusted sources should be strictly avoided or scanned prior to deployment.
Enforcing non-root user execution inside containers and utilizing security modules like AppArmor or SELinux adds defense-in-depth protection.
Impact:
Successful exploitation allows complete container escape and root-level privilege escalation on the host operating system.
Attackers can access sensitive files, compromise other containers, and execute arbitrary commands across the entire underlying infrastructure.
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Sources:
Reported By: github.com
Extra Source Hub:
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